Suppression of defect propagation in semiconductors by pseudomorphic layers
The propagation of defects in semiconductor heterostructures has been studied both theoretically and experimentally. The simple model shows that defects originating from lattice‐matched regions can be prevented from entering, or can be trapped by, a pseudomorphic layer, depending on the signs of the strain induced by the defect and the strain in the pseudomorphic layer. A pseudomorphic layer can therefore prevent the defect from propagating across in and entering the critical active region of a device. Experimentally, the photoluminescence intensities of Al0.4Ga0.6As/GaAs quantum wells with and without pseudomorphic In0.2Ga0.8As layers for prevention of defect propagation have been compared. GaAs substrates of high etch pit density were used to generate defects below the quantum well and silicon implantation was used to generate defects above it. The elevated temperatures during molecular‐beam‐epitaxial growth and postimplant rapid thermal annealing serve to assist in defect propagation in the respective ...
p-channel, strained quantum well, field-effect transistor
A p‐channel field‐effect transistor with a 3.5 μm Cr/Au gate was fabricated from a modulation‐doped GaAs/In0.2Ga0.8As/GaAs quantum well structure. Well‐behaved transistor action was observed at both 300 and 77 K with extrinsic transconductances of 6.2 and 11.3 mS/mm, respectively. Shubnikov–deHaas measurements prove the existence of a two‐dimensional hole gas with a strain‐shifted light‐hole ground state associated with a light‐hole mass of 0.154m0.
Corrections to the expression for gain in GaAs
When the expressions for gain derived in various papers are compared, a number of inconsistencies are found to exist. These inconsistencies have propagated through the literature and continue to do so. This study is specifically devoted to explaining how these inconsistencies originated so that they will not be repeated in future work on the subject. A general discussion of the matrix element is given, including spin degeneracy considerations, the procedure typically used in estimating the magnitude of the momentum matrix element, as well as the enhancement of the matrix element in quantum well structures. The correct expression for gain and spontaneous emission in semiconductors is given for comparison purposes within the framework of Fermi's golden rule. >