The individual subband densities and mobilities in delta -doped GaAs at different temperatures

摘要

The transport properties of delta -GaAs (Si) at high temperatures were studied using the 'mobility spectrum' technique. Strong changes in the subband occupancies were observed in a low-doped sample (ND=1.5*1012cm-2) as the temperature increased from 77 K to 300 K while in a high-doped sample (ND=5.0*1012cm-2) these changes were small. For an explanation of the observed behaviour with temperature Poisson's and Schrodinger's equations were solved self-consistently. The mobility of the lowest subband (i=0) was found to be relatively independent of temperature while the mobilities of the higher subbands (i>0) decreased with increasing temperature in both low- and high-doped samples. At close to room temperature, the conductivity of the delta -structures can be described well by a two-carrier model where the first group consists of the electrons of all the higher subbands having approximately equal mobilities.