E1 ELECTROLYTE ELECTROREFLECTANCE OF GAAS MODELED BY FRANZ-KELDYSH THEORY

Electrolyte electroreflectance spectra at the E1 transition were measured for <100> p-type GaAs electrodes of dopant density 2 x 10(16), 7 x 10(16), 2.7 x 10(17), and 2 x 10(18) cm-3. The spectra broadened with increasing reverse bias and increasing dopant density, which we believe to result directly from the increasing strength of the dc electric field, in contrast to the more usual assumption of low field conditions at the E1 transition. The intermediate field or Franz-Keldysh theory of Aspnes for a three dimensional M1 critical point has therefore been used to model the E1 and E1 + DELTA(1) features as a function of dopant density and depletion layer voltage. For values of the collision broadening parameter, GAMMA, measured by other workers under low field conditions, it is shown that significant field induced broadening is expected and that spectra can be successfully modeled, provided the collision broadening is allowed to increase fairly rapidly with increasing energy.