Temperature dependence of the equilibrium hall concentration in silicon planar-doped GaAs samples

Hall concentration and mobility were measured on nine MBE grown silicon planar-doped GaAs samples as a function of the temperature in the range of 20 to 300K. Al planar-doped layers were buried in undoped GaAs layers, and all the GaAs layers were 0.20 mu m thick, except one that was 0.50 mu m. A 60 Angstrom or 80 Angstrom n(+)-GaAs cap layer was used in all samples. The nominal silicon concentration varied in the range hem 1.4x10(12)cm(-2) to 8.1x10(13)cm(-2). We found that, for measurements carried out in darkness and for temperatures below about 200K, the Hall carrier concentration n(Hall) decreases for increasing temperature. We propose a two-subband model that allows an excellent fitting to the Hall measurements. According to the model, the decrease of n(Hall) results from thermally induced changes of the relative occupation of the subbands in the planar-doped well. Copyright (C) 1996 Published by Elsevier Science Ltd