Optical Gain Calculation of Wurtzite GaN/AlGaN Quantum Well Laser

Abstract

Optical gain properties of wurtzite GaN/Al0.2Ga0.8N quantum well lasers are theoretically analyzed using physical parameters from ab initio calculations for the first time. The valence band of wurtzite GaN exhibits strong non-paraboticity, and the hole density of states is significantly large in comparison with the conventional zincblende crystals. This valence band feature causes high transparency cartier density of 7.5×1018 cm-3 in the 50 Å thick GaN quantum well. This result predicts that the threshold current of wurtzite GaN/AlGaN quantum well laser is higher than the conventional lasers with zincblende crystals.

Reflectance spectroscopy on GaN films under uniaxial stress

“…This feature results in a large density of states ͑DOS͒ at the VBM, and thus, in a large threshold current density in GaN-based LDs. 3 From such an aspect, introduction of strain seems to be one of the most promising ways to reduce the DOS for improvement of laser performance. It has been predicted theoretically that uniaxial strain in the c plane should be effective in reducing the DOS.…”

Effects of electron beam annealing on optical and structural properties of GaN nanorods grown by HVPE

“…The vertical irradiation of e-beam onto the selected area of 100 nm  100 nm can cover only a single nanorod whereas the e-beam-irradiated area of 50 mm  50 mm will cover not only the individual nanorods but also the exposed strained layer due to the separation of each nanorod. Thus, the observation of CL peak at higher energy region is attributed to large amounts of signals from the strained layer because the blue-shift in emission properties is normally explained by the effect of biaxial strains [8][9][10].…”

“…It is well known that the energy band gap of a semiconductor is affected by the residual strain and/or surface effect. Effects of biaxial strain on the band structure have been deduced [8] from theoretical calculations such as the first-principles [9,10]. The strain dependencies of band gap and exciton energies are known to be associated with transitions from separate valence bands at G point (k ¼ 0).…”

Effective-mass Hamiltonian for strained wurtzite GaN and analytical solutions

“…Although the general strain Hamiltonian near the zone center using the k-p method [8][9][10] had been presented including the strain effects in the 1960's, only some work has been done recently to apply the results to investigate the wurtzite GaN/AlGaN quantum wells with strain effects. 11,12 Based on the theory of Luttinger-Kohn 8 and BirPikus, 9,10 the valence-band structure of a strained bulk wurtzite semiconductor, which includes the spin-orbit interaction effects under the cubic approximation, can be described by a 6ϫ6 Hamiltonian in the envelope-function space. The details of the elements of the Hamiltonian can be found in Refs.…”

“…Note that both K t and H t are real in our chosen bases. Some differences in the basis functions and signs in the previous references [9][10][11][12] have been corrected 14 here. For quantum-well structures, we can convert k z to Ϫi‫ץ/ץ‬z and solve for the coupled differential equations to obtain the wave functions and subband dispersions.…”