RAMAN CHARACTERIZATION OF AN OPERATING INALAS-INGAAS-INP HIGH ELECTRONIC MOBILITY TRANSISTOR

Raman scattering was used to probe electronic properties in In-based structures. First, Raman signatures of undoped and doped InAlAs and InGaAs bulk materials and Raman spectra of InAlAs-InGaAs heterostructures were recorded. Raman scattering by coupled longitudinal optic phonons and two-dimensional electron gas provides a powerful probe of electronic properties in this structure. More precisely, Raman results allowed information to be obtained on the two-dimensional gas electron carrier concentration. Then, a specific advantage of the micro-Raman method was demonstrated by the observation of the carrier concentration in the vicinity of the gate of an operating high electronic mobility transistor (HEMT). Qualitative variations of carrier concentration in the two-dimensional electron gas were observed and compared successfully with carrier concentration calculations using Monte Carlo simulations.