Nondestructive evaluation of carrier concentration in the channel layer of In0.5Ga0.5P/In0.2Ga0.8As/GaAs heterostructure field-effect transistors by Raman scattering

Carrier concentration (N) in the channel layers of pseudomorphic In0.5Ga0.5P/In0.2Ga0.8As/GaAs heterostructure field-effect transistors (HFETs) is evaluated by Raman scattering measurements. The coupled mode between the InGaAs longitudinal optical phonons and electrons in the InGaAs channel shifts continuously to a low wave number with an increasing N in the InGaAs channel. Preliminary calculation indicates that N can be determined with an error of less than 0.35 x 10(18)/cm(3) in the 10(18)/cm(3) order range, which corresponds to a 100 mV HFET threshold voltage. Raman scattering measurement is nondestructive and has a high spatial resolution as small as 1 mu m in diameter. Thus, this measurement is promising in HFET wafer selection, (C) 1998 American Institute of Physics.