In 1957 Herbert Kroemer published a paper entitled “Quasi-Electric and Quasi-Magnetic Fields in Non-Uniform Semiconductors". In it he expressed the utility of non-uniform semiconductor alloys in exploiting their natural atomic potential gradients to imply quasi-electric fields. The breakthrough in Modulation Doped Field Effect Transistors ( or MODFETs) came from the ground-breaking work done by him and Zhores Alferov on Semiconductor hetero-structures that utilize these very fields. I will examine just Herbert’s findings.
The objective is to study the effect of different experimental parameters on the reconstruction of the density of states (DoS) and to verify the viability of the 1D/2D simulation model developed at GeePs. Beside the calculation of the DoS through the modulated photo-current method (MPC), the ambipolar minority carrier diffusion length is measured through steady state photocarrier grating (SSPG) and the majority carrier lifetime / mobility product is measured through steady state photo-conductivity (SSPC). The measurements were observed to be in agreement with the theoretical simulations, but further experiments are needed to accurately conclude the need of a 2D simulation for the MPC experiment.