Optical determination of carrier density in pseudomorphic AlGaAs/InGaAs/GaAs hetero-field-effect transistor structures by photoluminescence

Abstract

A photoluminescence (PL) analysis of a highly degenerate two-dimensional electron gas (2DEG) in pseudomorphic modulation-doped AlGaAs/InGaAs/GaAs transistor structures is reported. The PL response from samples with one or two populated electron subbands is dominated by one or two spectral bands, respectively, with a high-energy intensity cutoff. The spectral width varies linearly with the measured 2DEG sheet density ns or with a Schottky barrier depletion voltage, which directly reflects the two-dimensional density of states (2DDOS) below the Fermi level. We used the effective electron mass from cyclotron resonance experiments to evaluate the 2DDOS and can thus directly determine ns from the spectral width via the 2DDOS. Independent ns values were obtained from Shubnikov–de Haas measurements and agree excellently with ns values from PL.