We investigated photoionization of deep traps in AlGaAs/GaAs multiple-quantum-well layers and measured the photocurrent (PC) parallel to the layers under a small electric field. There is a small shoulder due to the photoionization of a deep trap on the low-energy side of the n=1 exciton resonance peak in the PC spectra taken as a function of the excitation energy ℏω. The excitation energy dependence f(ℏω) and amplitude A of the photoionization cross section, σ(ℏω)=Af(ℏω), are determined by the time constants of single-shot PC transients. The excitation energy dependence increases linearly with excitation energy. The photoionization threshold energy EMQWth and the amplitude A increase as well thickness decreases. These characteristics are explained well by our theoretical study on the photoionization of a deep trap to subbands.
A theoretical crystal-field model for the X-(X = 0, S) centres with U,-symmetry leads to three equivalent operators for the np' 'P ground state, from which the g tensor of the defects can be calculated analytically. Three equivalent operator coefficients p , q , r a r e fitted to four a priori independent experimental quantities g,,, g",, gzz and q . This leads to an excellent agreement for NaCl: S-, RbCl : 0-and KCI : 0 -, and to a fair agreement for KCI : S -.
The donor-cation vacancy complex in Si-doped AlGaAs grown by metalorganic chemical vapor deposition has been identified by examining the growth-condition dependence of photoluminescence (PL) spectra. It has been revealed that the complex has the same origin as the self-activated center in GaAs, and is relevant to the degradation of crystal quality for high doping and high V/III ratio conditions. The excitation intensity dependence of PL spectra, and the fact that the emission is not observed for the samples with indirect gaps, suggest that the emission is a band-to-acceptor transition. The temperature dependence of the emission intensity and linewidth are compared with GaAs.
On the basis of a model which assumes a laminar boundary layer, a rate equation is derived for the vapor phase epitaxial growth of
normalGaAs
within a constant temperature zone. The equation can be used to predict the variation of growth rate with distance along the substrate. The predictions of the equation are shown to be in excellent agreement with the experimental results obtained with the open‐tube
AsCl3‐normalGa‐N2
system. It is also shown both theoretically and experimentally that the variation of growth rate decreases with increasing gas velocity and also with decreasing substrate temperature, whereas the initial
AsCl3
mole fraction has no effect on the growth rate variation.
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