Piezoelectric field effects in InGaAs (111)B quantum wells

Abstract

Strained In0.21Ga0.79As/GaAs quantum well structures have been grown by molecular beam epitaxy on (111)B GaAs substrates. Well widths between 20 and 160 Å, separated by 500 Å barriers were grown sequentially on the same substrate and subsequently characterized by low-temperature (10 K) photoluminescence. The variation of the e-hh transition energy with well width is markedly different for samples grown simultaneously on (100) and (111)B substrates due to the strain induced piezoelectric field. Using the envelope function approximation, the dependence of n=1 e-hh transitions of (111)B samples on well width can be interpreted by the presence of a built-in electric field of magnitude of 1.45×107 V/m. In contrast to the (100) sample, exciton lifetimes in the (111)B sample depend strongly on well width because of spatial separation of electrons and holes in the triangular wells. In the 160 Å well, the exciton lifetime increases to 755 ns corresponding to a reduction of about three orders of magnitude in the electron-hole wave function overlap integral.