Self-consistent calculations and magnetoluminescence studies of strained InP/In_xGa_1-xAs heterojunctions

We have self-consistently calculated the energy levels, subband populations, and envelope wave functions for a two-dimensional electron gas (2DEG) in an n-type modulation doped InP/In_xGa_(1-x)As heterojunction as a function of the composition (x value). By comparing the theoretical results with low-temperature photoluminescence (PL) measurements on compressive, tensile, and lattice-matched n-type modulation-doped InP/In_xGa_(1-x)As samples, we were able to verify the calculated results and thus also identify the observed PL emission peaks and suggest a probable potential profile across the In_xGa_(1-x)As layer. From Shubnikov–de Haas measurements on Hall bars, we have independently determined the subband population in all investigated samples. The measured subband populations increase with increasing In content, and are in fair agreement with the self-consistently calculated values. We have also performed PL and PL excitation (PLE) spectroscopy in the presence of a perturbing magnetic field. In these measurements we observed the formation and linear shift of Landau levels (LL’s) in the 2DEG when we applied an increasing magnetic field. From a linear least-square fit to the PL peak position of the LL’s in magnetic fields up to 4.4 T, we deduced the following reduced effective masses for the lowest observable subband; 0.0416±0.001, 0.0445±0.003, and 0.0443±0.005 for the compressive (x=0.62), tensile (x=0.46), and unstrained (x=0.53) samples, respectively. In the PLE measurements we observed excitonic transitions at higher energies that are related to the 2DEG, and show nonlinear shifts versus increasing magnetic field. © 1996 The American Physical Society.