Interface disorder in GaAs/AlGaAs quantum wells grown by molecular beam epitaxy at high substrate temperature

Abstract

The interface disorder of quantum wells grown by molecular beam epitaxy at high substrate temperature is investigated by low-temperature photoluminescence. The excitonic emission from a single quantum well is a single sharp peak, and the well width precisely determined from the emission peak energy does not equal to integral multiples of one-monolayer width in almost all samples. These results indicate that the lateral size of growth islands with a one-monolayer height is much smaller than the exciton diameter and a one-monolayer interface acts as a layer with smaller AlAs mole fraction than the barrier layer.

Optical properties of AlAs/GaAs quantum wells with antimony as a surfactant by solid source molecular beam epitaxy

“…2 shows the room-temperature PL spectrum for samples A, B, C, and D. The PL spectra show the increased energy peak of emission with decreasing well width due to the quantization effect. In sample A, only excitonic transitions from the QWs are displayed and the peak is from the transition between the first electron and heavyhole states (e 1 -hh), indicating that the lateral size of grow islands is not as large as the exciton diameter ($150 Å ) [14]. In samples B, C, and D, two distinct peaks are clearly observed in an 8 nm thick QW, which corresponds to transitions of the first electron to heavy hole (e 1 -hh) and electron to light hole (e 1 -lh).…”

“…1(a) and (b) show the 24 K PL spectrum and linewidths for samples A, B, C and D as a function of photon energy, respectively. For sample A (without Sb used), only excitonic transitions from the QWs are displayed and the peak is from the transition between the first electron and heavy-hole states (11 H), indicating that the lateral size of grow islands is not as large as the exciton diameter ($150 Å ) [14]. For samples B, C, D (Sb used), the PL peak shapes of the 8 nm QWs exhibit a shoulder on the low-energy side.…”

“…For samples B, C, D (Sb used), the PL peak shapes of the 8 nm QWs exhibit a shoulder on the low-energy side. The double-line PL emission from 8 nm QW is unlikely to originate from the electron to heavy hole (e-hh) or electron to light hole (e-lh) transition because the splittings (about 2 meV) are too small, which indicates that the terrace widths are larger than the exciton diameter ($150 Å ) [14]. The PL linewidths are increasing from thicker to thinner QWs, due to the greater effect of the interface roughness.…”

Sharp Exciton Photoluminescence in Low-Temperature-Grown GaAs/AlGaAs Multiple Quantum Wells

“…9,13,14) As is well known, the PL linewidth of a QW exciton is dominated by phonon scattering and inhomogeneous broadening due to interface roughness and alloy disorder. [13][14][15][16] Interface roughness generates inhomogeneous broadening on exciton peaks due to fluctuations of well width. The alloy disorder results in a nonrectangular or rounded well, which causes a shift of exciton energy levels to higher energies.…”

Optical study of heterointerface configuration in narrow GaAs/AlGaAs single quantum wells prepared with growth interruption

“…It is well known that growth interruption at either one or both heterointerfaces in molecular-beamepitaxy ͑MBE͒ growth can improve the interface smoothness and make the luminescence line split due to the formation of growth islands with a lateral size much larger than the freeexciton Bohr diameter. [1][2][3][4] Based on the early luminescence work, these extended growth islands had been claimed to be atomically smooth and abrupt; 1,2 however, the later studies questioned the validity of the ''atomically smooth island'' picture and suggested that the island size distribution is bimodal. [5][6][7] In other words, there exists a large amount of microroughness with its length scale below the exciton diameter superimposed on top of the large islands.…”