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Communication

Onset of Quantum-Confined Stark Effects in Multijunction Photovoltaic Laser Power Converters Designed with Thin Subcells

by
Simon Fafard
* and
Denis Masson
Broadcom (Canada), IFPD, Ottawa, ON K1A 0R6, Canada
*
Author to whom correspondence should be addressed.
Photonics 2023, 10(11), 1243; https://doi.org/10.3390/photonics10111243
Submission received: 27 September 2023 / Revised: 2 November 2023 / Accepted: 6 November 2023 / Published: 8 November 2023
(This article belongs to the Special Issue Latest Papers Related to OWPT 2023 on the Topics of Devices, Components and Systems)
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Abstract

:
Photovoltaic multijunction power-converting III–V semiconductor devices generate electrical power from the optical energy of laser beams. They exhibit conversion efficiencies reaching values greater than 60% and 50% for the GaAs and the InP material systems, respectively. The applications of optical wireless power transmission and power-over-fiber greatly benefit from employing such laser power converters constructed with multiple subcells; each is designed with either thin GaAs or InGaAs absorber regions. This study elucidates how the application of electric fields on thin heterostructures can create specific current–voltage characteristics due to modifications of the absorption characteristics from Franz–Keldysh perturbations and the onset of quantum-confined Stark effects. Negative differential photocurrent behavior can be observed as the reverse bias voltage is increased, until the corresponding current-clamping subcell reaches its reverse breakdown condition. The reverse voltage breakdown characteristics of the subcells were also measured to depend on the thickness of the subcell and on the optical intensity. The onset of the reverse breakdown was found to be at ~2.0–2.5 V under illumination and the thinner subcells exhibited higher levels of reverse bias currents. These effects can produce distinctive current–voltage behavior under spectrally detuned operations affecting the thinner subcells’ biases, but have no significant impact on the performance and maximum power point of multijunction power converters.

1. Introduction

It is well established that the optical properties of semiconductor materials are affected by electric fields. In bulk III–V materials, the Franz–Keldysh effect generates a tail in the absorption coefficient below the absorber’s bandgap, as well as spectral oscillations of the absorption coefficient for energies above the absorber’s bandgap value. Similarly, in low-dimensionality semiconductor structures, the corresponding quantum-confined Stark effect also modifies the material’s absorption coefficient. These effects have been thoroughly studied and exploited [1,2,3,4,5,6,7,8,9,10,11], especially in GaAs and InP-based devices benefiting from electric-field controlled electro-absorption properties in quantum wells made of GaAs or InGaAs absorbers. Concurrently, p/n photovoltaic (PV) devices have been optimized to convert laser power at different wavelengths [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91]. Such devices are usually called Optical Power Converters (OPCs) or Laser Power Converters (LPCs) and have been shown to greatly benefit from heterostructure designs based on multiple subcells [12,48] instead of a thicker single p/n junction. This is because the voltage generated by an OPC or LPC increases with the number of series connected layers or subcells used in its design. For that reason, multijunction LPCs can be thought of as Photo-Transducers (PT for short), where the number of subcells determines the output voltage of the devices when subjected to illumination. Thus, a device built from a stack of a number, N, of light absorbing p/n junctions of the same type (e.g., all GaAs p/n junctions) is expected to generate an output voltage approximately N times the voltage of one p/n junction. It is convenient then to refer to the active layers of OPCs and LPCs as PTN where PT refers to photo-transducer and N, the number of active absorbing p/n junctions used. Note that the highly doped p++/n++ tunnel junctions often used in OPCs and LPCs are usually designed with materials having a bandgap higher than the bandgap of the absorbing material (i.e., transparent to the incident optical beam). Therefore, the tunnel junctions do not contribute to the output voltage, except for a very small internal drop in voltage (typically only a few mV). The ability to design and fix the output voltage from the beginning is important for most practical applications where a specific voltage range is usually required and/or when the voltage and current must match the intended load impedance.
In the approach using series-connected subcells discussed above, a comparable fraction of the incident optical beam is absorbed in each subcell and the Beer–Lambert law is used as a good first approximation to design the individual thicknesses of the p/n junctions thus comprised of a stack of thinner subcells [22,23]. It should also be noted that for a given optical input wavelength, the total absorber thickness required to capture substantially all (e.g., 99%) the incident light is fixed. Therefore, PTN LPCs built with a larger N value are by design constructed with thinner subcells. Concurrently, PTN devices with different N values have similar total device thicknesses.
Compared to its constituent absorber material, such series-connected layers efficiently convert a high-power optical input, with a relatively narrow spectral range, into an electrical output. The output has an up-converted photovoltage and a correspondingly down-converted current in operation [42,43,44]. For a specified incident laser wavelength, a photocurrent-matching condition is realized by design, with the subcells having increasing thicknesses from the top subcell (thinnest) toward the bottom subcell (thickest). LPC devices with 12 subcells or more have been successfully realized. As the number of subcells is increased, the upper subcells need to be thinner than 100 nm [43,44,45]. The physics of these multijunction power converter devices is interesting with phenomena such as strong luminescence coupling and recycling [57,58,59,60], especially when the device is operated in de-tuned conditions, away from the peak of its spectral response. The study of spectrally de-tuned multijunction LPCs, designed with thin absorbing subcells, is therefore of particular interest to better understand the influence of applied electric fields on the properties of these devices. In addition, in typical p/n junctions, potential Franz–Keldysh effects occur in the depletion zone where the electric field is the strongest. Since the depletion zone is determined by doping levels rather than the overall thickness, the effects are expected to be more pronounced in thinner cells.
The present study demonstrates that the application of electric fields on heterostructures incorporating thin GaAs and InGaAs subcells can create distinctive current–voltage (I–V) characteristics. Negative differential photocurrent behavior can be observed as the bias voltage is swept from the photovoltaic (positive biases) to the photodiode (negative biases) mode of operation, until the corresponding current-clamping subcell reaches its reverse breakdown condition. Control single junctions (1Js) of different thicknesses are also studied and our overall results indicate that the observed negative differential photocurrent behavior of the multijunction device is due to modifications of the absorption characteristics from Franz–Keldysh or the onset of quantum-confined Stark effects. The results also confirm that these effects have no significant impact on the maximum power point of multijunction power converters while producing distinctive I–V behavior under spectral detuned operations.

2. Materials and Methods

The heterostructures are grown lattice-matched using commercial production Metal Organic Chemical Vapor Deposition (MOCVD) reactors from Aixtron. For the present study, the photovoltaic junction designs were all n/p, i.e., based on an n-type emitter nearest to the incident side of the light input. The LPCs with the GaAs absorbers are grown on GaAs substrates. They have AlGaAs and InGaP-based barriers and tunnel junctions between the subcells’ absorber regions [22]. For consistency, the thicknesses and doping levels of the tunnel junctions were kept substantially equivalent for the various multijunction designs with a different number of subcells. The longer-wavelength LPCs with the InGaAs absorbers are grown on InP substrates. They have InP and AlInGaAs-based barriers and tunnel junctions between the surbcells’ absorber regions [46]. Manufacturing microfabrication processes are used to transform the epitaxial wafers into chips. A chip area of ~0.03 cm2 is used here. The chips have corner pads and a contour busbar. The devices include standard blanket back-metallization, front ohmic contacts, and antireflection coatings (ARCs). The ARC is constructed from layers of Al2O3 and TiO2 and typically reduces the reflectivity (R) of the incident beam to R < 4% for the spectral range of interest. From our overall experimentation, the details of the chip geometry are not particularly relevant to the specific phenomenon discussed in this study. The I–V characteristics were acquired with a Keithley 2601B source meter in the 4-wire probing mode. For the I–V measurements, the tip of a fiber-coupled laser was positioned in front of the device at near-normal incidence. The distance between the fiber tip and the PV device was adjusted to obtain the desired spot size from the diverging beam. Therefore, as is usually the case in typical operating conditions, non-uniform illumination is used in the experiments of this study [48]. The fiber laser had a numerical aperture of ~0.22. The input lasers were operated in a continuous (CW) mode. Quick I–V scans were used to minimize any chip heating or temperature drifts between the measurements.

3. Results

Control 1Js of different thicknesses were also prepared using the processes described above. The related heterostructure details have been described in detail previously [22]. The thicknesses of the five control 1Js devices were between 212 nm and 2336 nm, as indicated in Figure 1 and Figure 2. Figure 1 shows the measured dark I–Vs for all five 1Js, together with the 808 nm illuminated I–V characteristics for the thinnest control GaAs single junction: S5, having a thickness of 212 nm. Figure 2 shows the semi-log plot of the dark I–V curves of Figure 1 to better visualize the relative dark-current behavior of the 1Js designed with different thicknesses.
The illuminated I–Vs of Figure 1 are obtained with optical input powers between 0.1 W and 0.5 W. The diode equation fits (model) to the illuminated I–V curves are shown with the dotted curves. Good fits can be obtained using an ideal diode equation for the forward voltages V > 0. For simplicity, the reverse breakdown behavior is characterized by a power-law breakdown for V < 0:
I ( V )   =   − I sc   +   I o   [ e x p ( q V / n k T )   −   1 ] , V   ≥   0 I ( V )   =   − I sc −   α   V   −   V br β ,   V   <   0
where Isc is the zero-bias photocurrent or equivalently the short-circuit current, Io is the saturation current, n is the ideality factor, q is the charge of the electron, k is the Boltzmann’s constant, T is the temperature; and α, β, and Vbr are empirical values used to characterize the breakdown current behavior. Ideality factors of n = 1.6 were used because values around 1.6 gave close to the best fits to the I–V curves, especially for the voltages between Vmpp and Voc.
The onset of the reverse breakdown was in the range of negative ~2.0 to 2.5 V for the GaAs PV cells, depending on the illumination intensity. Moreover, the thinner subcells exhibit higher levels of reverse bias currents, as evidenced in Figure 2. Therefore, the reverse voltage breakdown characteristics of the subcells were measured to depend not only on the subcell thickness, but also strongly influenced by the incident optical intensity, as can be deduced from Figure 1 and Figure 2.
It should also be noted that the subcell electrical field and the p/n depletion region width are expected to be influenced primarily by the doping levels and can also be affected by screening effects [7,8] from the photocarrier density. Precise quantitative modeling of these effects is beyond the scope of the present study. However, the control 1J device characteristics measured in Figure 1 and Figure 2 can now be used to benchmark and better understand the behavior of multijunction LPCs.
Figure 3 compares the I–V characteristics of multijunction GaAs devices with a number of N = 6, 8, and 10 subcells, hereby named PTN with N representing the number of subcells, as mentioned in the introduction. The peak of the spectral response of these LPCs was separately measured to be between 815 nm and 835 nm, with peak conversion efficiencies in excess of 60% [12,45,48].
The optical input for Figure 3 was intentionally detuned by using a laser probe wavelength of 850 nm, with 0.25 W of optical input power. With the detuning being on the long wavelength side of the peak of the spectral response, the multijunction devices are therefore unambiguously current-limited by the upper subcell for a bias voltage around the maximum power point of their respective I–V curves: Vmpp = 10.35 V for the PT10, Vmpp = 8.35 V for the PT8, and Vmpp = 6.40 V for the PT6. As the applied voltage is swept in the reverse direction, away from Vmpp on the I–V curves, the current-clamping of the current-limiting subcell is maintained until the subcell reverse current breakdown is reached. Then, the next subcell becomes current-limiting and clamps the overall multijunction current. This cascade continues until all subcells are in reverse-breakdown mode. Consequently, the I–V curves of the multijunction devices feature the same number of current plateaus as the corresponding number of subcells. Indeed, 6, 8, and 10 plateaus are clearly observed in Figure 3 for PT6, PT8, and PT10, respectively. Similar plateaus have been reported previously. By biasing the multijunction device on a given plateau, the relative photocurrent of the corresponding subcell can be extracted at the probing wavelength. This method can be useful for extracting the responsivity, the quantum efficiency, the absorption coefficients, and the spectral response information for the heterostructure [18,31,32,40,41,44].
Figure 3 also shows the diode equation fits to the illuminated I–V curves. The fits are shown with the overlapping dotted curves and incorporate N series-connected subcells based on Equation (1). As for the control 1Js, ideality factors of n = 1.6 were used for the fits. Moreover, the α, β, and Vbr fitting values for the breakdown current behaviors used in Figure 3 are consistent with the behavior observed in Figure 1 for the control 1Js. For the PTN devices, the thicknesses of the thinnest upper subcells were further reduced to 127 nm, 120 nm, and 106 nm for the PT6, PT8, and PT10, respectively. By comparing the ideal diode fit to the measured I–V behaviors, it becomes apparent that slight photocurrent reductions are sometimes observed before the onset of the subcell’s reverse-bias breakdown. Such negative differential photocurrent behavior can be observed more clearly with the first plateau of the PT10 for the thinnest upper subcell (i.e., 106 nm). The photocurrent is reduced by ~6% as the reverse bias voltage is increased, until the corresponding current-clamping subcell reached its reverse breakdown condition. This is not expected from the ideal diode equation model. It justifies further analysis because, for the measured condition, such a photocurrent decrease suggests a reduction in the absorption coefficient under the applied electric field. The effect is further investigated in Figure 4 with PT12 having an even thinner upper subcell of 82 nm.
Figure 4 shows the measured I–V characteristics of a PT12 multijunction GaAs device with 12 subcells. The black curve shows the responsivity for a detuned condition on the short wavelength side of the peak of the spectral response. Under these conditions, the device is unambiguously current-limited by the thicker bottom subcells (here, 2211 nm thick). The observed plateaus are substantially flat, as expected for subcells with no significant changes to their absorption properties caused by applied electric fields. In drastic contrast, the green curve is for a detuned condition on the long wavelength side of the peak of the spectral response, and therefore current-limited by the thinner top subcells. For the 82 nm subcell (peak between 9 V and 12 V of the green curve), significant negative differential photocurrent behavior can be observed as the reverse bias voltage is increased, until the corresponding current-clamping subcell reaches its reverse breakdown condition. It is worth pointing out that the effect was exemplified here with 12 subcells, but similar behavior has also been measured for devices with more subcells (e.g., PT20, not shown), or slightly lower number of subcells such as the PT10 of Figure 3.

4. Discussions

We observed that the negative differential photocurrent behavior is apparently enhanced for the thinner subcells (i.e., PTN with larger N). This is combined with the observation that these features are substantially absent for the conditions when the device is current-limited by the thicker bottom subcells (i.e., for a detuned condition on the short wavelength side of the peak of the spectral response). It strongly suggests that the thinner subcells support these particular I–V characteristics due to modifications of the absorption characteristics from Franz–Keldysh perturbations or the onset of quantum-confined Stark effects [4,11].
Similar behavior is also clearly observed for the other material system studied. These LPCs are using InGaAs as the absorbing subcells. They are for applications at wavelengths around 1.5 μm. For example, Figure 5 shows a semi-log plot of the measured I–V characteristics of a PT10 multijunction device with 10 InGaAs subcells lattice-matched to InP. For this heterostructure, the thickness of the thinnest upper subcell is 105 nm.
The curves probed at 1466 nm correspond to the nearly spectral-matched situation. In these almost current-matched conditions, each subcell generates a similar fraction of photocurrents and it cannot clearly be determined specifically which subcell is current-clamping the entire heterostructure. Relatively flat I–V characteristics are obtained, even in the reverse-bias conditions. A top conversion efficiency of 51.7% was obtained for an input of 1.5 W at 1466 nm (orange curve) [46]. Furthermore, the output power reaches 1.02 W when the input power is increased to 2 W (black curve).
Figure 5 also shows the I–V measured for a detuned condition at 1547 nm, represented by the pink curve. This is on the long wavelength side of the peak of the spectral response, therefore current-limited by the thinner top subcell at a voltage bias around the maximum power point (Vmpp = 5.1 V). Very similar to the GaAs PT10 or PT12, here also for the InGaAs/InP PT10, significant negative differential photocurrent behavior can be observed for the first few plateaus. The photocurrent slightly decreases as the reverse bias voltage is increased, until the corresponding current-clamping subcell reaches its reverse breakdown condition.
The 1547 nm laser had a maximum of 6 mW of optical output because it is a single-mode laser diode with limited output capabilities. However, other measurements (not shown) carried out at higher optical powers with a multimode ~1550 nm laser diode revealed similar behaviors, comparable to the results shown in Figure 5 at 1547 nm (pink curve).

5. Conclusions

We have studied photovoltaic multijunction power-converting heterostructures with thin subcells. In this study, comparable results have been obtained covering different material systems in the near-infrared: using GaAs absorbers (spectral range between 800 nm and 850 nm), and similarly using InGaAs absorbers (spectral range between 1450 nm and 1550 nm). The observed effects are therefore clearly not specific to a given material system. The influence of the thickness of the thin absorbing subcells has also been systematically investigated by probing multijunction devices with different numbers of thin subcells. Probe wavelengths below the peak of the spectral response, near the peak of the spectral response, and above the peak of the spectral response have been investigated. It allows to unambiguously obtaining conditions with current-limited bottom subcells, near current-matched, and current-limited top subcells respectively.
Near the peak of the spectral response of the heterostructure, top conversion efficiencies were obtained. They are capable of converting high-power laser beams into electrical power with conversion efficiencies reaching greater than 60% and 50%, for the GaAs and the InP material systems, respectively. Relatively flat I–V characteristics are then obtained, even for the large reverse-bias conditions.
For optical inputs at wavelengths shorter than the peak of the spectral response, plateaus are observed in the I–V curves, as expected for subcells exhibiting reverse-bias breakdown behaviors. The reverse voltage breakdown characteristics of GaAs control of single junction subcells were separately confirmed to depend on the thickness of the subcell and on the incident optical intensity. The thinner subcells exhibit higher levels of reverse bias currents.
In contrast, for optical inputs at wavelengths longer than the peak of the spectral response, the plateaus in the I–V curves can be slightly distorted. The effect was observed to be more pronounced when the thinnest (upper) subcells have thicknesses of ~100 nm or smaller (i.e., PTN devices with larger N). Our results suggest that the application of electric fields on thin heterostructures can result in such distinctive I–V characteristics due to modifications of the absorption characteristics from Franz–Keldysh perturbations or the onset of quantum-confined Stark effects. For the thin subcells, negative differential photocurrent effects were observed until the corresponding current-clamping subcell reached its reverse breakdown condition.
For such thin subcells, the n-type emitter and the p-type base are typically designed to be individually about half of the thickness of the subcell. The built-in field of the n/p junction therefore divides the absorber into three regions. The high-field region in the middle of the subcell, and on either side, regions forming electrons and holes with confinement potentials under the reverse bias conditions. The electron confinement potential is formed in the conduction band, nearest to the input side of the incident beam, between the built-in field and the conduction band discontinuity of the n-type cladding material. The hole confinement potential is formed in the valence band, opposite to the input side of the incident beam, between the built-in field and the valence band discontinuity of the p-type cladding material.
Characteristically, during the onset of the quantum confined Stark effect, the absorption edge of the absorber is red-shifted while typically the absorption coefficient decreases for energies above the shifted band-edge. The observed negative differential photocurrent effects are therefore consistent with such an onset of the quantum confined Stark effect.
Importantly, it should be noted that the negative differential photocurrent effects observed and described in this study do not significantly affect the maximum power point of multijunction optical power converters.

Author Contributions

Conceptualization, S.F. and D.M.; methodology, S.F. and D.M.; software, S.F. and D.M.; validation, S.F. and D.M.; formal analysis, S.F. and D.M.; investigation, S.F. and D.M.; data curation, S.F. and D.M.; writing—original draft preparation S.F.; writing—review and editing S.F. and D.M.; visualization, S.F.; project administration, S.F. and D.M.; funding acquisition, S.F. and D.M. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflict of interest, but it should be noted that the authors are employed by Broadcom, a company that manufactures and sells semiconductor components, including power converter devices.

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Figure 1. Measured I–V characteristics for thin control GaAs single junctions having different absorber thicknesses: dark-S1 is the dark I–V curve for a GaAs absorber 2336 nm thick, dark-S2 is for 581 nm, dark-S3 is for 346 nm, dark-S4 is for 246 nm, and dark-S5 is for 212 nm. Measured I–V curves are shown for S5 illuminated at 808 nm with optical input powers between 0.1 W and 0.5 W. The diode equation fit (model) to the illuminated I–V curves is shown with the dotted curves for each optical input power. The device area is 0.034 cm2. The dark-S1, dark-S2, dark-S3 and dark-S4 lines follow near the zero current horizontal axis, but are clearly revealed in Figure 2 using a logarithmic current axis.
Figure 1. Measured I–V characteristics for thin control GaAs single junctions having different absorber thicknesses: dark-S1 is the dark I–V curve for a GaAs absorber 2336 nm thick, dark-S2 is for 581 nm, dark-S3 is for 346 nm, dark-S4 is for 246 nm, and dark-S5 is for 212 nm. Measured I–V curves are shown for S5 illuminated at 808 nm with optical input powers between 0.1 W and 0.5 W. The diode equation fit (model) to the illuminated I–V curves is shown with the dotted curves for each optical input power. The device area is 0.034 cm2. The dark-S1, dark-S2, dark-S3 and dark-S4 lines follow near the zero current horizontal axis, but are clearly revealed in Figure 2 using a logarithmic current axis.
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Figure 2. Semi-log plot of the dark I–V curves of Figure 1.
Figure 2. Semi-log plot of the dark I–V curves of Figure 1.
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Figure 3. I–V characteristics of multijunction GaAs devices for 6, 8, and 10 subcells (named PTN with N representing the number of subcells). The I–V curves are measured with 0.25 W of optical input at 850 nm, detuned on the long wavelength side of the peak of the spectral response: i.e., current-limited by the upper subcells. The thicknesses of the thinnest upper subcells are: 127 nm, 120 nm, and 106 nm for PT6, PT8, and PT10 respectively. The diode equation fit to the illuminated I–V curves is shown with the dotted curves for each device. The area of the devices is 0.032 cm2.
Figure 3. I–V characteristics of multijunction GaAs devices for 6, 8, and 10 subcells (named PTN with N representing the number of subcells). The I–V curves are measured with 0.25 W of optical input at 850 nm, detuned on the long wavelength side of the peak of the spectral response: i.e., current-limited by the upper subcells. The thicknesses of the thinnest upper subcells are: 127 nm, 120 nm, and 106 nm for PT6, PT8, and PT10 respectively. The diode equation fit to the illuminated I–V curves is shown with the dotted curves for each device. The area of the devices is 0.032 cm2.
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Figure 4. Measured I–V characteristics of a PT12 multijunction GaAs device with 12 subcells. The responsivity curves are measured with 0.25 W of optical input power, the device area is 0.032 cm2 and the thickness of the thinnest upper subcell is 82 nm. The black curve is for a detuned condition on the short wavelength side of the peak of the spectral response: i.e., current-limited by the thicker bottom subcells. The green curve is for a detuned condition on the long wavelength side of the peak of the spectral response: i.e., current-limited by the thinner top subcells.
Figure 4. Measured I–V characteristics of a PT12 multijunction GaAs device with 12 subcells. The responsivity curves are measured with 0.25 W of optical input power, the device area is 0.032 cm2 and the thickness of the thinnest upper subcell is 82 nm. The black curve is for a detuned condition on the short wavelength side of the peak of the spectral response: i.e., current-limited by the thicker bottom subcells. The green curve is for a detuned condition on the long wavelength side of the peak of the spectral response: i.e., current-limited by the thinner top subcells.
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Figure 5. Measured I–V characteristics of a PT10 multijunction device with 10 InGaAs subcells lattice-matched to InP. The I–V curves are measured at the wavelengths and optical input powers indicated. The device area is 0.032 cm2 and the thickness of the thinnest upper subcell is 105 nm. The 1466 nm curves are for the nearly spectral-matched condition and the pink curve is for a detuned condition at 1547 nm, on the long wavelength side of the peak of the spectral response: i.e., current-limited by the thinner top subcells.
Figure 5. Measured I–V characteristics of a PT10 multijunction device with 10 InGaAs subcells lattice-matched to InP. The I–V curves are measured at the wavelengths and optical input powers indicated. The device area is 0.032 cm2 and the thickness of the thinnest upper subcell is 105 nm. The 1466 nm curves are for the nearly spectral-matched condition and the pink curve is for a detuned condition at 1547 nm, on the long wavelength side of the peak of the spectral response: i.e., current-limited by the thinner top subcells.
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Fafard, S.; Masson, D. Onset of Quantum-Confined Stark Effects in Multijunction Photovoltaic Laser Power Converters Designed with Thin Subcells. Photonics 2023, 10, 1243. https://doi.org/10.3390/photonics10111243

AMA Style

Fafard S, Masson D. Onset of Quantum-Confined Stark Effects in Multijunction Photovoltaic Laser Power Converters Designed with Thin Subcells. Photonics. 2023; 10(11):1243. https://doi.org/10.3390/photonics10111243

Chicago/Turabian Style

Fafard, Simon, and Denis Masson. 2023. "Onset of Quantum-Confined Stark Effects in Multijunction Photovoltaic Laser Power Converters Designed with Thin Subcells" Photonics 10, no. 11: 1243. https://doi.org/10.3390/photonics10111243

APA Style

Fafard, S., & Masson, D. (2023). Onset of Quantum-Confined Stark Effects in Multijunction Photovoltaic Laser Power Converters Designed with Thin Subcells. Photonics, 10(11), 1243. https://doi.org/10.3390/photonics10111243

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