Effect of uniaxial stress on photoluminescence in GaN and stimulated emission inInxGa1−xN

Abstract

Photoluminescence and stimulated emission ͑SE͒ in a wurtzite GaN bulk crystal and In x Ga 1Ϫx N/GaN multiple quantum wells ͑MQW's͒ are investigated under uniaxial stress applied perpendicularly to the c axis. The strain in GaN induces a decrease in the photoluminescence intensity of B excitons relative to A excitons due to an increase in the energy splitting between the two states. In In x Ga 1Ϫx N/GaN MQW's, SE and optical gain in the localized states are observed at 6 K under low excitation power below the Mott density of excitons. The uniaxial stress induces a low-energy shift of the gain peak and a decrease in the threshold carrier density of SE. In the excitation power above the Mott density, the SE arises from an electron-hole plasma recombination. The gain value at 0.43 GPa is 1.34 times as large as that without stress at 6 K, which is comparable with a theoretical estimation. The observed effects of strain are ascribed to a decrease in the density of states at the valance-band maximum.

NaCl-assisted substrate dependent 2D planar nucleated growth of MoS2

“…Furthermore, mica has a layered structure and inter-layer van Der Waals bonding, that may favour the growth of monolayer MoS2 having hexagonal structure too. Ichimiya et al 34 reported that higher the stress, lesser would be A/B exciton ratio. So, these points clearly explain that 1L-MoS2 grown on sapphire has the highest quality PL followed by 1L-MoS2/mica, while 1L-MoS2 on SiO2/Si has the lowest (Fig.…”

Highly polarized photoluminescence from c-plane InGaN/GaN multiple quantum wells on stripe-shaped cavity-engineered sapphire substrate

“…It has been theoretically and experimentally reported that c-plane GaN-based semiconductors under anisotropic in-plane strain (uniaxial strain perpendicular to c-axis) exhibited modified valence band structures and resultant optical properties 31–33 . Therefore, if it is possible to simply render and control the in-plane strain states in continuous c-plane InGaN/GaN MQWs grown on c-plane sapphire substrate, the linearly polarized emission with high efficiency could be realized at an affordable production cost.…”

Superfluorescence of Sub-Band States in C-Plane In0.1Ga0.9N/GaN Multiple-QWs

“…C-plane InGaN/GaN quantum wells (QWs) as the prevailing active layer have been studied extensively due to their promising applications in group-III nitride semiconductor optoelectronic devices [ 1 , 2 , 3 , 4 ]. Commonly accepted explanations for emission features are the spatial localization of carriers due to random alloy fluctuations, indium compositional fluctuations and well width fluctuations [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], the quantum-confined Stark effect (QCSE) because it spatially separates electron and hole wave functions and reduces the wave function overlap in the QWs [ 19 , 20 , 21 , 22 , 23 , 24 , 25 ] and the screening of the QCSE under a high excitation that affects the excitation density-dependent emission energy of InGaN/GaN MQWs, for example, a very strong emission from quantum-dot-like states [ 26 ], high energy emission band [ 27 , 28 , 29 ] and stimulated emission on the high-energy side in thick QWs [ 30 , 31 , 32 ].…”