ELECTRON-MOBILITY IN GASB

The effect of carrier concentration and compensation on the electron m obilities in GaSb at 300 and 77 K are investigated. Since the energy o f the L band minima relative to the Gamma band minima in GaSb is repor ted to range from 0.075 to 0.09 eV, electrons are present in significa nt amount in both the Gamma and L bands at about 150 K and above. Thus , in addition to the impurities and phonons scattering, non-equivalent and equivalent intervalley scattering in both conduction bands are al so included in the 300 K calculation. To compare the calculated Hall m obility with the various 300 K experimental data consistently, the ele ctron mobilities in the Gamma and L bands are combined using a two ban d model. This is because experimental electron Hall mobility and elect ron concentration determined above 150 K are weighted averages of the true values in the two conduction bands. It is found that the correlat ion for the heavily doped bulk samples are good while for the lighter doped thin epilayers, the calculated mobilities are at least 20% highe r. We attribute this to several effects present in the real samples an d the growth conditions which are not taken into consideration in the calculations. The 77 K highly doped bulk and best MBE data are also fo und to correlate reasonably well with the calculated values. We have a lso numerically fitted all the electron mobilities calculated to a lth polynomial in carrier concentration which may facilitate device model ling.