PHOTOLUMINESCENCE EVALUATION OF PSEUDOMORPHIC HIGH-ELECTRON-MOBILITY TRANSISTOR DEVICE WAFERS

Photoluminescence (PL) has been used for some time in the evaluation of pseudomorphic high electron mobility transistor material structures. Among the results routinely obtained from these structures are estimates of electron sheet density in the InGaAs channel, either from empirical relationships or from first principles (from direct observation of the Fermi level). We present a semiempirical line shape model for the study of PL line shapes at low temperatures. We show that the primary source of error for optical measurement of the sheet density is in the filling of the channel by electrons injected by the incident laser. We also demonstrate the potential for extraction of structural parameters such as channel composition and thickness from careful observation of variations in PL transition energies.