HYDROSTATIC-PRESSURE DETERMINATION OF TENSILE-STRAINED GAXIN1-XP-(ALYGA1-Y)(0.52)IN0.48P QUANTUM-WELL BAND OFFSETS

Photoluminescence, measured as a function of hydrostatic pressure, has been used to determine the band offsets of two tensile-strained GaxIn 1-xP-(AlyGa1-y)(0.52)In0.48P quantum-well structures. Unlike other tec hniques commonly used to determine band offsets, this method has the a dvantage that a detailed knowledge of the material parameters is not r equired. Conduction-band offsets of Delta E(c) = (0.79 +/- 0.07)Delta E(G)(HH) and Delta E(c) = (0.74 +/- 0.10)Delta E(G)(HH), where Delta E (G)(HH) is the total heavy-hole-related band-gap discontinuity, are ob tained for structures having strains of + 0.56 and + 0.71% and barrier Al compositions of 0.7 and 0.55, respectively. Alternatively the band offsets expressed in terms of the light-hole band-gap discontinuity a re Delta E(c): Delta E(G)(LH) = 0.70:0.30 and 0.61:0.39 [corresponding to absolute light-hole valence-band offsets of Delta E(V)(LH) = (110 +/- 12) meV and (113 +/- 15) meV] for the + 0.56 and + 0.71% strained samples, respectively. At high pressures the structures become type II , and the observed indirect real and k-space transition exhibits a blu eshift with increasing incident laser power density. An analysis of th is blueshift allows both the density and lifetime of the spatially sep arated photoexcited carriers to be determined.