Measurement of Enhanced Inversion Factor of InGaAs-Based Well-Island Composite Structure by Photoluminescence Spectra from Dual Facets

Abstract

The inversion factor is an important physical parameter for assessing and revealing the performance of semiconductor lasers, providing insights into the carrier-injected band-filling effect and radiation characteristics. In this paper, the carrier inversion factor (P_f) is measured to elucidate the luminescence mechanism of an InGaAs-based well-island composite (WIC) structure, formed by the self-assembly migration of indium atoms and exhibiting excellent spectral properties. P_f is obtained by collecting the amplified photoluminescence (PL) spectra from dual facets of the device, with carrier concentrations ranging from 9.0 × 10¹⁷ to 9.4 × 10¹⁷ cm⁻³. Compared with classical InGaAs/GaAs quantum well structures under the same operating conditions, the inversion level in the WIC structure can be as high as 2.2. Simulation results reveal enhanced quasi-Fermi-level separation and broadened spectral bandwidth. The research is of great significance in the development of new types of quantum-confined lasers with wide spectral output.

1. Introduction

Due to their outstanding optoelectronic properties, InGaAs/GaAs semiconductor lasers adopting the classical quantum well (QW) structure as the active region have been widely applied in fields such as communications, optical sensing, medical devices, etc. [1,2,3,4,5]. Particularly for the special InGaAs-based well-island composite (WIC) structure that has emerged in recent years, it exhibits excellent optical characteristics, demonstrating significant application potential in the field of novel optoelectronic devices. Specifically, this structure enables the realization of polarization-independent semiconductor optical amplifiers (SOAs) by providing nearly identical TE and TM modal gains. It is achieved through a hybrid strain state blending HH₁/LH₁ contributions, further enhanced by surface morphology effects that reduce optical transition sensitivity to crystal orientation [6]. Moreover, dual-wavelength lasing on a single chip is achieved owing to the distinctive step-like band structure, which allows for independent carrier recombination in discrete active regions [6,7]. The stability of the WIC structure has been confirmed by photoluminescence (PL) spectra as well as the stable dual-wavelength lasing. The special WIC structure arises from the Indium-rich cluster (IRC) effect during the growth of the highly strained InGaAs/GaAs material system. The IRC formation mechanism is primarily driven by the migration of indium atoms along the growth direction of InGaAs materials, resulting from the significant lattice mismatch ratio and sufficient strain accumulation. The strain-induced migration of indium atoms results in the atomic accumulation and the formation of three-dimensional (3D) nanoclusters, specifically, IRCs on the material surface [8,9,10]. Consequently, the migration of indium atoms leads to the reduction of indium contents in the corresponding InGaAs regions, resulting in the coexistence of normal and indium-reduced In_xGa_1−xAs regions within a single InGaAs active region. The mechanism triggers the formation of a unique energy band structure, characterized by the enhanced inversion factor and the broadened spectra with dual peaks, distinguishing it from the classical QW structure. The carrier inversion factor, P_f, serves as a significant physical parameter for analyzing the carried-injected band-filling effect and Fermi-Dirac inversion distribution, offering valuable insights into the emission characteristics of WIC nanostructures. However, current studies on carrier inversion factors and carrier distribution properties mainly focus on the classical QW structure rather than the special WIC nanostructure [11,12,13,14,15,16]. Furthermore, several drawbacks are associated with the methods involved in such studies, such as the introduction of segmented electrodes and non-uniformity of the carrier distribution within each section, caused by carrier diffusion between segments. This increases the complexity of measurement methods and the inaccuracy of experimental results. This paper investigates the carrier inversion factor by collecting amplified PL spectra from the dual facets of the device to further reveal the luminescence mechanism of the broadened spectra with dual peaks. This study presents the first measurements and analysis of P_f in the special WIC structure.

In this paper, a special WIC nanostructure is obtained according to the strain-induced migration of indium atoms. Then, the experimental setup and theoretical framework for measuring the carrier inversion factor P_f of the WIC structure are established by collecting the PL spectra from the dual facets. Based on the PL spectra from the WIC structure derived by an 808 nm fiber-coupled semiconductor laser as the excitation source, the carrier inversion factor with different carrier densities of 9.0 × 10¹⁷, 9.2 × 10¹⁷, and 9.4 × 10¹⁷ cm⁻³ is obtained. Finally, the luminescence mechanism and band-filling level of the WIC nanostructure are further elucidated through comparative analysis of the P_f and energy band structure of classical QW structures. The results not only reveal the broadened gain characteristics of the WIC structure but also provide an important theoretical foundation for optimizing the design of next-generation semiconductor lasers.

2. Experimental Methods

2.1. The Preparation of In_xGa_1−xAs-Based WIC Nanostructure

Extensive studies on indium-rich clusters (IRCs) have demonstrated that indium atoms tend to migrate along the growth direction as a strain relaxation mechanism, driven by the considerable strain within InGaAs material. This migration acts to alleviate the accumulated strain energy inherent in highly mismatched heterostructures. Accordingly, the indium composition x and the thickness L_z of the In_xGa_1−xAs layer emerge as the primary parameters governing the formation and spatial distribution of IRCs, since they directly influence the extent of strain built-up within the active region [9,10]. Based on our previous studies [10], the suitable range for forming a stable WIC structure is an indium content of 0.15 ≤ x ≤ 0.2 and an active layer thickness of 8 ≤ L_z ≤ 12 nm. Therefore, the initial indium composition of x = 0.17 and a thickness of L_z = 10 nm are selected. The active region was designed with a material composition of In_0.17Ga_0.83As/GaAs/GaAsP_0.08, where the initial indium content in the In_xGa_1−xAs layer was set to x = 0.17 to ensure a sufficient lattice mismatch. Additionally, the thickness of the In_xGa_1−xAs layer was engineered to be 10 nm, providing adequate strain accumulation to drive the migration of indium atoms and promote the formation of IRCs. When the InGaAs layer exceeds a critical thickness, the pronounced strain within the In_0.17Ga_0.83As material induces an upward migration of indium atoms, leading to the development of three-dimensional (3D) clusters on the surface of the In_xGa_1−xAs layer as a strain-relief mechanism. Within this system, a 2-nm-thick GaAs strain-compensating layer is strategically inserted between the In_0.17Ga_0.83As active layer and the 8-nm-thick GaAsP_0.08 barrier layer. The GaAsP_0.08 barrier serves to efficiently absorb the pump light and facilitate the generation and confinement of photoexcited carriers in the active region. The In_xGa_1−xAs-based well-island composite (WIC) nanostructure was epitaxially deposited on GaAs (001) substrates via metal-organic chemical vapor deposition (V/III ratio: 40, growth rate: 0.75 µm/h, reactor pressure: 100 mbar, and substrate temperature: 660 °C). Trimethylindium (TEIn), trimethylgallium (TMGa), and arsine (AsH₃) were employed as source materials, with their flow rates precisely controlled at 600, 3000, and 180,000 μmol/h, respectively. Purified hydrogen gas (9N) was used as the carrier gas to ensure a clean growth environment. The elevated growth temperature was intentionally employed to enhance the surface diffusion length of indium atoms, thereby promoting the nucleation and growth of IRCs [17]. The corresponding WIC structure is illustrated in Figure 1a.

Initially, the growth mode of the In_0.17Ga_0.83As region follows an ideal two-dimensional (2D) pattern within several monomolecular layers due to minimal strain accumulation. The indium content of x = 0.17 remains fixed (Region Ⅰ in Figure 1b). However, as the thickness of the In_0.17Ga_0.83As layer exceeds a critical value, accumulated strain reaches a threshold, inducing the upward migration of indium atoms to release stress and generate an island-like appearance. Meanwhile, the migration of indium atoms leads to the reduction of indium contents in the corresponding In_0.17Ga_0.83As quantum well layer and formation of indium-reduced In_xGa_1−xAs region (Region Ⅱ in Figure 1b). The formation mechanism produces a distinctive WIC active region containing both areas with indium-normal In_0.17Ga_0.83As and indium-reduced In_xGa_1−xAs regions. Additionally, the three-dimensional morphology of the InGaAs surface is observed using an atomic force microscope (AFM). The measurement results, as shown in Figure 1c, indicate that the sizes and distribution of indium-rich clusters are generally random, which leads to significant lateral inhomogeneity in indium distribution [18]. The size of the IRCs can be evaluated as 50–200 nm in width and 2–8 nm in height, respectively. For simplicity, they can be roughly grouped into two size ranges: around 150 nm and 50 nm. The local indium content (x) in the InGaAs material decreases from the original x = 0.17 to two lower levels: x = 0.12 and 0.15 (Region Ⅱ in Figure 1b) [7]. This is because the degree of indium atom migration is gradually weakened with the gradual release of stress, and the indium content begins to recover.

2.2. Experimental Principle and PL Spectral Measurements

To measure and calculate the carrier inversion factor P_f of the InGaAs/GaAs WIC quantum-confined laser structure, we established an experimental setup to collect the photoluminescence (PL) spectra from the dual facets of the WIC sample, as illustrated in Figure 2. One facet of the sample was coated with an anti-reflectance coating (transmittance T = 99.99%) to eliminate intra-cavity light feedback, while the other facet remained uncoated, with a reflectance R. The epitaxial device was processed in an edge-emitting configuration with an area of 1.5 mm × 3 mm, which was optically pumped by an 808 nm fiber-coupled semiconductor laser with a pulse width of 20 ms (a product of Beijing Laserwave Optoelectronics Technology Co., Ltd. (Beijing, China), Model LWIRL808-40W-F). The PL spectra I_PL1 (left) from the coated facet of the device and I_PL2 (right) from the uncoated facet are collected by a spectrometer (Ocean Optics Inc. (Dunedin, FL, USA), model HR4000CG-UV-NIR), as shown in Figure 2, where the carrier densities are 9.0 × 10¹⁷ (red), 9.2 × 10¹⁷ (blue), and 9.4 × 10¹⁷ (black) cm⁻³. The carrier density N can be calculated from the pump power P_P by using the following equation [19]:

$$P_P={\displaystyle \frac{h\nu N_W{L}_W{A}_P(AN+B{N}^2+C{N}^3)}{{\eta }^{abs}}}$$

(1)

where η_abs is the absorption efficiency of the pump, hν is the photon energy of the 808 nm pumping laser. A, B, and C are the monomolecular, bimolecular, and Auger recombination coefficients. The above parameters for InGaAs material can be found in [19]. A_P is the pump spot area, which is designed to be 36 mm². N_W and L_W represent the number and thickness of the InGaAs layer, with values of 1 and 10 nm, respectively. The pump powers corresponding to the optically injected carrier densities of 9.0 × 10¹⁷, 9.2 × 10¹⁷, and 9.4 × 10¹⁷ cm⁻³ are 9.8, 10.3, and 10.7 W, respectively.

Unlike the single-peak spectra emitted from classical QW structures, the PL spectra exhibit obvious double-peak characteristics across various carrier densities. This distinctive feature arises from the indium-rich cluster (IRC) effect, which results in the coexistence of multiple active regions with different indium compositions. The multi-peak structure is attributed to emissions from normal and indium-reduced In_xGa_1−xAs regions. The indium-reduced In_xGa_1−xAs regions exhibit larger band gaps, forming high-energy localized quantum wells that greatly improve the limiting effect on the photo-generated carriers. This confinement effectively suppresses carrier escape, prolongs carrier lifetime, and significantly enhances radiative recombination efficiency in the short-wavelength region. This greatly improves the carrier inversion level. Additionally, Figure 2 shows that as the carrier concentration increases, the spectral peak (I_PL1) shifts slightly from 1.274 to 1.267 eV, and I_PL2 moves slightly from 1.272 to 1.268 eV. This shift arises from heat accumulation due to nonradiative recombination, resulting in bandgap shrinkage despite the implementation of a temperature control system [20].

2.3. Experimental Determination of Carrier Distribution

Different from previous experimental methods on carrier inversion factor in semiconductor lasers, this study investigates the carrier distribution properties in WIC structures by analyzing photoluminescence spectra collected from dual facets. According to the definition, the carrier inversion factor P_ƒ can be determined as the ratio of modal gain G and spontaneous emission intensity I_sp [11]. The value of P_ƒ at a particular photon energy, E_hv, reflects the degree of inversion of the states at energies E₁ and E₂ corresponding to that photon energy (E_hv = E₁ − E₂) and can be expressed as follows:

$$P_f(E_{hv}=E_1-E_2)={\displaystyle \frac{f_1(E_1)-f_2(E_2)}{f_1(E_1)[1-f_2(E_2)]}}=K{\displaystyle \frac{G(hv)}{I_{sp}(hv)}}$$

(2)

where the factors f₁(E₁) and f₂(E₂) are the occupation probabilities of the upper and lower states, respectively, which participate in the transition at photon energy E_hv = E₁ − E₂. K denotes the proportional factor. When the energy state is completely occupied by carriers, the corresponding occupancy probability f = 1. Conversely, the occupancy probability f = 0 if the energy state is empty. The inversion factor tends to -∞ at high photon energy, where the upper state is empty and the lower state is full. Conversely, P_f approaches 1 at low photon energies when the system is fully inverted, such that the upper state is completely occupied (f₁ = 1) and the lower state is completely empty (f₂ = 0). A fully inverted semiconductor system is thus characterized by the inversion factor P_f approaching unity (P_f → 1). Fundamentally, when the carrier distribution is inverted, the occupation probability of the upper energy state E₁ exceeds that of the lower energy state E₂ (i.e., f₁ > f₂), resulting in a positive P_f. This population inversion condition is essential for enabling efficient stimulated emission within the material.

The modal gain G and spontaneous emission intensity I_sp can be calculated according to the collected PL spectra using the equations [21]:

$$I_{PL1}={\displaystyle \frac{I_{sp}}{G}}(e^{GL}-1)(R{e}^{GL}+1)$$

(3)

$$I_{PL2}={\displaystyle \frac{I_{sp}}{G}}(1-R)(e^{GL}-1)$$

(4)

where I_PL1 and I_PL2 denote the PL intensities measured from the two lateral ends of the WIC sample. L is the distance of light transmitting through the sample in one pass. The facet reflectivity (R ≈ 30%) is mainly determined by the refractive index of the Al_0.08–0.15GaAs waveguide layer, since the active layer thickness (10 nm) is much smaller than the waveguide layer thickness (2 μm). The facet reflectivity can be calculated using the following equation:

$$R={\left({\displaystyle \frac{n_{AlxGa1-xAs}-n_{air}}{n_{AlxGa1-xAs}+n_{air}}}\right)}^2$$

(5)

where n_air is the air refractive index (~1), and n_AlxGa1−xAs represents the refractive index of the waveguide layer, ranging from 3.22 to 3.26. Based on Equation (5), the facet reflectivity is calculated to be R ≈ 0.3.

By combining Equations (3) and (4), the modal gain G can be derived as follows:

$$G={\displaystyle \frac{1}{L}}\ln {\displaystyle \frac{(1-R)I_{PL1}-I_{PL2}}{R\times I_{PL2}}}$$

(6)

The spontaneous emission intensity, I_sp can be expressed by substituting (6) into (4):

$$I_{sp}={\displaystyle \frac{{R{I}^2}_{PL2}}{L[{(1-R)}^2{I}_{PL1}-(1-R^2)I_{PL2}]}}\ln {\displaystyle \frac{(1-R)I_{PL1}-I_{PL2}}{R\times I_{PL2}}}$$

(7)

Combining Equations (2), (6), and (7), the carrier inversion factor, P_f can be described as:

$$P_f(E_{hv})=K{\displaystyle \frac{{(1-R)}^2{I}_{PL1}-(1-R^2)I_{PL2}}{R\times {I^2}_{PL2}}}$$

(8)

Thus, the carrier inversion factor P_f can be worked out using Equation (8) according to the PL spectra of I_PL1 and I_PL2 in Figure 2, which represent the intensity at each wavelength. The inversion factor of the WIC structure with the various carrier densities of 9.0 × 10¹⁷, 9.2 × 10¹⁷, and 9.4 × 10¹⁷ cm⁻³ is shown in Figure 3a, where the proportional factor K can be evaluated as about 0.016. The error of P_f at each photon energy was obtained by calculating the absolute difference between the original data and the Savitzky-Golay smoothed data (Polynomial Order: 2, Points of Window: 2 in Origin 2021 software).

To demonstrate the advantages of the WIC structure, the classical QW structure with no IRCs is established by PICS3D, with 10-nm-thick In_0.17Ga_0.83As material as the well layer, GaAs material as the strain compensation layer of 2 nm thickness, and GaAsP_0.08 material with 8 nm thickness as the barrier material. The structural parameters are similar to the WIC structure. The inversion factor (P_f) can be expressed as follows [11]:

$$P_f(E_{hv})=1-\exp \left({\displaystyle \frac{E_{hv}-\mathsf{\Delta }{E}_f}{K_{B}T}}\right)$$

(9)

where ΔE_f is the quasi-Fermi level separation between electrons and holes, K_B is the Boltzmann constant, and T is the temperature. The value of ΔE_f was determined by simulated material gain spectra (illustration in Figure 3b) by identifying the photon energy at which the material gain g = 0 (transparency point). Therefore, the P_f of the classical QW structure is shown in Figure 3b under similar carrier densities with the corresponding ΔE_f of 1.297 eV, 1.305 eV, and 1.313 eV.

3. Results and Discussion

According to (2), the inversion factor P_f depends solely on the occupation probabilities for the upper and lower states of the transition, f₁(E₁) and f₂(E₂), respectively. The necessary condition for stimulated emission in semiconductor materials is to achieve the inversion distribution of carriers. Therefore, the carrier’s degree of inversion will directly affect the spectral characteristics of semiconductor materials.

The experimental data for P_f in Figure 3a are unity at low photon energy, corresponding to complete population inversion (f₁(E₁) = 1, f₂(E₂) = 0). Regions exhibiting P_f > 0 correspond to the condition where f₁(E₁) > f₂(E₂), enabling efficient stimulated emission. Consequently, the energy separation E_hv = E₁ − E₂ matching the zero-crossing point (P_f = 0) fails to produce effective radiative recombination. This is because E₁ and E₂ cannot be effectively filled by electrons and holes. Therefore, the energy separation at P_f = 0 can be used to estimate the carrier-filling level. In Figure 3, when the carrier density increases from 9.0 × 10¹⁷ to 9.4 × 10¹⁷ cm⁻³ (4% increase), the band-filling level of the WIC structure increases from 1.352 to 1.392 eV (3.0% enhancement), while that of the classical QW structure increases from 1.297 to 1.313 eV (1.2% enhancement), indicating that WIC structure has higher carrier-filling capacity. Furthermore, compared to classical QW structures, the WIC structure can maintain P_f > 0 at the high-energy side, primarily due to the indium-reduced InGaAs regions, which exhibit the wide band gaps and create the localized high-energy quantum wells. It significantly enhances the probability of carriers occupying high-energy states, enabling effective carrier inversion at the high-energy side. To further investigate the carrier’s degree of inversion, the energy range of carrier inversion distribution (left vertical axis) with P_f > 0 between the special WIC structure and classical QW structure is presented in Figure 4a based on Figure 3. Specifically, the photon energy corresponding to P_f = 0 is first identified from Figure 3, followed by the photon energy 1.24 eV for P_f = 1. The difference between these two energy values is taken as the inversion range shown in Figure 4a. Besides, the ratio (right vertical axis) was also obtained by comparing the inversion ranges between the WIC and QW structures.

Figure 4a clearly shows that the inversion range (0.11, 0.13, and 0.15 eV) of the WIC structure (blue, experimental results) exhibits a broader value compared to that (0.05, 0.06, and 0.07 eV) of the classical QW structure (red, simulation results) under the carrier concentrations of 9.0 × 10¹⁷, 9.2 × 10¹⁷, and 9.4 × 10¹⁷ cm⁻³. The carrier’s degree of inversion in the WIC structure is up to 2.2 times larger than that of the classical QW structure. This indicates a significant increase in the probability of carriers occupying the upper state. Consequently, the WIC structure achieves higher carrier band-filling levels, which leads to the wide spectral bandwidth compared to classical quantum well (QW) structures. For a more comprehensive comparison, the simulated spectra from both WIC and QW structures are shown in Figure 4b. The WIC structure is established by COMSOL Multiphysics software (v6.1), with 4-nm-thick In_0.17Ga_0.83As, 4-nm-thick In_0.12Ga_0.88As, and 2-nm-thick In_0.15Ga_0.85As materials as the active layer, GaAs material as the strain compensation layer of 2 nm thickness, and GaAsP_0.08 material with 8 nm thickness as the barrier material. For the QW structure, all layer parameters are identical to those of the WIC structure, except that the active layer consists of 10-nm-thick In_0.17Ga_0.83As. The results demonstrate that the classical 10-nm In_0.17Ga_0.83As QW exhibits a single spectral peak with a bandwidth of 42.8 nm, whereas the WIC structure shows two distinct peaks with a broadened bandwidth of 74.8 nm. The WIC structure exhibits higher spectral intensity in the short-wavelength region, indicating that carriers are easier to occupy high-energy levels, resulting in an enhanced P_f. This significantly enhances radiation recombination efficiency in the high-energy side, which is in agreement with our experimental results. This phenomenon is primarily attributed to the coexistence of normal and indium-reduced In_xGa_1−xAs regions, resulting from the strain-induced migration of indium atoms. The indium-reduced In_xGa_1−xAs regions, with larger band gaps, make it easier for carriers to occupy the high-energy levels, thereby increasing carrier inversion and band-filling levels, which can greatly expand the spectral bandwidth. To better demonstrate the WIC structure’s advantages in carrier inversion distribution and spectral characteristics, Figure 5 presents theoretically calculated energy band structures for both WIC and QW designs, simulated using COMSOL Multiphysics’ Semiconductor Module with a 2D steady-state drift-diffusion model that incorporates carrier transport, self-consistent potential distribution, and heterojunction boundary conditions. The migration of indium atoms induces nonuniform distributions of indium contents along both the growth and the horizontal directions. This complex distribution feature cannot be precisely represented in band diagrams. Therefore, Figure 5a presents a simplified band model, which simplifies a large number of discrete regions into three regions along the growth direction: In_0.17Ga_0.83As, In_0.12Ga_0.88As, and In_0.15Ga_0.85As to reveal the enhancement mechanism of the carrier inversion factor.

Figure 5a shows the WIC’s band structure with regions of three different band gaps, leading to the improved Fermi distributions of the carriers, which arise due to the IRC effect. Based on our previous study [22], the thicknesses can be evaluated as approximately 4 nm for normal In_0.17Ga_0.83As and 6 nm for indium-reduced In_xGa_1−xAs layers. In this paper, the thicknesses of In_xGa_1−xAs layers with x = 0.17, 0.12, and 0.15 are estimated to be 4, 4, and 2 nm, respectively. The band gap of In_0.12Ga_0.88As is greater than that of In_0.15Ga_0.85As, which is larger than that of In_0.17Ga_0.83As, resulting in step-like sub-bands. These indium-reduced regions exhibit larger band gaps, forming high-energy localized quantum wells. It is beneficial to limit the photo-generated carriers in upper energy states. It improves both the degree of inversion and carrier-injected band-filling ability at high-energy states and then emits high-energy photons to expand the spectral bandwidth. Additionally, the quasi-Fermi levels (E_fn and E_fp) of electrons and holes are also calculated, which serve as a significant physical parameter in characterizing the carrier-filling level and Fermi-Dirac inversion distribution [23,24,25]. It can be clearly observed that the quasi-Fermi-level separation ΔE_f of the WIC structure (0.93 eV) can be as high as 1.09 times that of the classical QW structure (0.85 eV), reflecting the significant advantages of the WIC structure in carrier distribution and gain bandwidth. This implies that carriers are easily transitioned to high-energy states for radiative recombination, thereby improving the effective radiation level spacing and spectral bandwidth. These regions not only increase the probability of carriers occupying high-energy states but also increase the q-Fermi level separation, resulting in an enhanced inversion factor. The improved inversion factor promotes carrier recombination in high-energy states, resulting in a broadened gain bandwidth. The result is of great significance in the development of new types of quantum-confined lasers with wide spectral output. Despite demonstrating promising application potential, this structure remains in the fundamental research stage, requiring further development and rigorous evaluation of its performance under practical application conditions.

4. Conclusions

In this paper, a special InGaAs/GaAs well-island composite (WIC) nanostructure is obtained based on the indium-rich cluster effect during the growth of a highly strained InGaAs/GaAs material system. The inversion factor of the optically pumped In_xGa_1−xAs WIC structure is obtained according to the photoluminescence (PL) spectra collected from both ends of the WIC epitaxial device. The analysis of carrier distribution data reveals that the degree of inversion in the WIC structure can be up to 2.2 times higher than in classical QW structures over the same carrier concentration range of 9.0 × 10¹⁷ to 9.4 × 10¹⁷ cm⁻³. Additionally, the simulated spectra and band structure demonstrate that the WIC structure exhibits a higher quasi-Fermi-level separation and carrier-filling level. This suggests that carriers are more easily inverted into high-energy states, which in turn facilitates the emission of spectra with a broader bandwidth. The findings of this research are of significant importance for the development of next-generation quantum-confined lasers with wide spectral outputs.