Measurement of 'material' parameters in multi-quantum-well structures

Abstract

Multi-quantum-well (MOW) structures can be regarded as new materlals whose properties are determined by the well and barrier thicknesses 1, and Le and the well depth (which is composition dependent). Measurements of L,, L e and x are reported for 16 MQW samples grown by molecular beam epitaxy in the AI,Gal-x~s system. Results from x-ray diffraction, photoluminescence excitation spectroscopy and transmission electron microscopy are found to compare well with each other and with values predicted from MBE growth conditions.

2D-GaN/AlN Multiple Quantum Disks/Quantum Well Heterostructures for High-Power Electron-Beam Pumped UVC Emitters

“…QW width fluctuations in the ML range were initially studied in the 1980s for GaAs/AlGaAs QW structures [ 58 , 59 , 60 , 61 ]. In these works, the ML fluctuations were much smaller than the nominal well width (about 10–20 nm).…”

Does In form In-rich clusters in InGaN quantum wells?

“…The localisation energy is typically only a few meV, and so localisation by this mechanism only occurs at low temperature in GaAs/AlGaAs [29].…”

High resolution transmission electron microscopy and three-dimensional atom probe microscopy as complementary techniques for the high spatial resolution analysis of GaN based quantum well systems

“…The localisation energy is typically only a few meV, and so localisation by this mechanism only occurs at low temperature in GaAs/AlGaAs. 19 However, the localising effects of well width fluctuations are much greater in the InGaN/GaN QW system, both because the InGaN is more highly strained and because the piezoelectric effect is much stronger than in GaAs/AlGaAs.…”

“…Atomic force microscopy (Fig. 6) reveals the epilayer to consist of a network of interlinking strips of material, 50-100 nm wide, aligned roughly along the [11][12][13][14][15][16][17][18][19][20] direction. Cross-sectional HRTEM has been used to show that the troughs between the strips penetrate through the full thickness of the epilayer.…”

“…Cross-sectional EDX measurements have been used to check the variation in indium content across the strips. Figure 8a shows an STEM HAADF image of a single InGaN strip, viewed along the [11][12][13][15][16][17][18][19][20][21] zone axis. Analyses of EDX have been performed at each of the positions indicated by the numbered crosses, and the results are shown in Fig.…”