SELF-CONSISTENT CALCULATIONS AND MAGNETOLUMINESCENCE STUDIES OF STRAINED INP INXGA1-XAS HETEROJUNCTIONS/

We have self-consistently calculated the energy levels, subband popula tions, and envelope wave functions for a two-dimensional electron gas (2DEG) in an n-type modulation doped InP/InxCa(1-x)As heterojunction a s a function of the composition (x value). By comparing the theoretica l results with low-temperature photoluminescence (PL) measurements on compressive, tensile, and lattice-matched n-type modulation-doped InP/ ln(x)Ga((1-x))As samples, we were able to verify the calculated result s and thus also identify the observed PL emission peaks and suggest a probable potential pro tile across the InxGa(1-x)As layer. From Shubni bov-de Haas measurements on Hall bars, we have independently determine d the subband population in all investigated samples. The measured sub band populations increase with increasing In content, and are in fair agreement with the self-consistently calculated values. We have also p erformed PL and Pi, excitation (PLE) spectroscopy in the presence of a perturbing magnetic field. In these measurements we observed the form ation and linear shift of Landau levels (LL's) in the 2DEG when we app lied an increasing magnetic held. From a linear least-square fit to th e FL peak position of the LL's in magnetic fields up to 4.4 T, we dedu ced the following reduced effective masses for the lowest observable s ubband; 0.0416 +/- 0.001, 0.0445 +/- 0.003, and 0.0443 +/- 0.005 for t he compressive (x = 0.62), tensile (x = 0.46), and unstrained (x = .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.