Theoretical analysis of optical polarization properties in semipolar and nonpolar InGaN quantum wells for precise determination of valence‐band parameters in InGaN alloy material

Abstract

In order to make a precise determination of InGaN material parameters (valence-band A parameters and deformation potentials), reported experimental data on polarization properties have been analyzed by the kÁp perturbation theory, in which we utilized fact that the polarization properties are sensitive to the material parameters. It is found that the polarization properties are largely affected by the deformation potentials while the valence-band A parameters have small effects. In addition, it is found that two deformation potentials' sets roughly fit with the reported experimental data. From the calculation using these two parameters' sets, it is predicted that low-angle semipolar substrate orientation (u ¼ 308-408) are promising for low-cost and high-performance green laser diodes with cleaved facet cavity mirrors. These results support our previous prediction based on analytical calculations. 1 Introduction Utilization of InGaN quantum wells (QWs) on non-c-crystal planes for active layers of green laser diodes (LDs) has attracted attention, because internal electronic field can be reduced in the QWs [1]. In these structures, in-plane optical anisotropy appears, and optical gain is concentrated into one particular direction. Thus, the optical polarization properties have to be considered for the structural design of laser devices. In general, there are two bands at the top of the valence bands in InGaN material system, and one of them has X 1 -like character and the other has X 2 -like, where the X 1 direction is the normal direction to the c-axis on the substrate plane, and the X 2 direction is the projection of the c-axis on the substrate plane, as shown in Fig. 1(a). Polarization properties are mainly determined by the energy difference (DE) between X 1 -and X 2 -like bands shown in Fig. 1(b). Thus, the value of DE can be an index of the polarization properties (e.g., positive sign of DE means that emission is polarized in the X 1 direction). In our previous paper, we reported that these polarization properties are dependent on the substrate orientations and QW

Optical polarization properties of (11–22) semi-polar InGaN LEDs with a wide spectral range

“…For the longer wavelength LEDs above ~470 nm the polarization degree therefore switches to a negative sign (ρ < 0) which signifies that the intensity of the polarized emission along the [−1-123] direction is now higher than that of the polarized emission along the direction. This is entirely consistent with previous studies 19,25,26 . As the emission moves towards longer wavelength, the polarization degree becomes larger in the negative direction owing to the larger energy separation of the two topmost | ′>…”

Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

“…This VCSEL was also measured to have a 100% polarization ratio, as reported in our previous study, 38 due to the intrinsic nature of the splitting of the first and second valence subbands, and the anisotropy of the valence band orbitals (i.e., transition matrix element interaction strength) on m-plane. 45,46,63,64 Comparing this device to our previous reported device, which employed a SiN x aperture, we see a $5Â reduction in J th , which is likely due to the use of the ion implanted aperture. Furthermore, the overall yield of these devices is markedly higher than we observed previously, though we still see a large variation in the J th across a single chip.…”

“…37,38 Beyond the lack of the quantum confined Starke effect (QCSE) in m-plane multi-quantum wells (MQWs), m-plane is advantageous to c-plane due to the lower transparency carrier and current densities, 39,40 higher material gain, [41][42][43][44] and anisotropic gain characteristics. [41][42][43][44][45][46] The anisotropic gain allows one to achieve a 100% polarization ratio, 38 which can be useful in many applications. Here, we present our recent progress in nonpolar m-plane VCSELs, showing a $5Â decrease in the threshold current density, which is primarily attributable to the use of a planar ITO design, enabled by an Al ion implanted aperture.…”

Precise determination of deformation potentials in InGaN alloy material in semipolar and nonpolar InGaN quantum wells

“…In addition, the anisotropy of valence-band A parameters was also neglected, because it has been found, in our previous study, that the anisotropy are not that large, and that ΔE is mainly determined by the strain effects. 20) Equation (1) shows that the ΔE is determined by the in-plane strain anisotropy (the first term) and the anisotropy of deformation potentials (the second term). Since D i 's, c ij 's, and e  take constant values in InGaN-QWs with the same In composition coherently grown on GaN substrates, ΔE is considered as a function of substrate orientation for InGaN-QWs with the constant In composition.…”