Warm and hot hole drift velocity in GaAs studied by Monte Carlo simulation

Abstract

Monte Carlo calculation of the electron drift velocity in GaAs with a superlatticeWe have studied hole mobilities and drift velocities in undoped GaAs at 77 and 300 K using the Monte Carlo method. Two different sets of valence band parameters were used ( Vl: A = 7.98, B = 5.16, C = 6.56; V2: A = 7.65, B = 4.82, C = 7.7). The results show that the low-field mobility is sensitively dependent on the particular choice of valence band parameters. The low-field mobilities obtained were 440 cm'/V s( Yl) and 330 cm'/V s(m) at 300 K, and 17 150 cm2/V s( Vl ) and 11400 cm2/V s( V2) at 77 K. The warm hole transport coefficients /3s and y. were extracted from the drift velocity data. At 77 K, PO = -7 X 10 -9 m2/V2 and y. was estimated to be 2x 10 -lo m2/V2( Vl). At 300 K the corresponding estimated values were -2X10-13 m2/V2 and 5X lo-i4 m2/V2, respectively. The warm hole region is limited to E ~0.04 kV/cm at 77 K and to &< 10 kV/cm at 300 K. Anisotropy in the drift velocity is negligible in the warm hole region and relatively small at higher electric fields. Complete velocity saturation was not observed for the electric fields considered here (E < 60 kV/cm) .

Monte Carlo simulation of impact ionization and current multiplication in short GaAs diodes

“…This is largely due to the greater flexibility of the analytical model in allowing better fitting with its many parameters. Our analytical model is obviously incapable of treating anisotropy, though these effects are not large either for electron or hole transport [12,26,34] and this approach is consistent with the well known isotropy of the impact ionization process at high fields [11,17].…”

“…Similarly, the reason for omitting band warping is the exaggerated effect that uncertainties in the inverse band parameters have at higher energies (particularly noticeable in Si [25]) and also because of the known isotropy of GaAs hole mobility at high fields [12] which would seem to indicate the possibility of applying a spherical approximation. The hole masses were, however, generated by averaging over all directions using the inverse band parameters of Brudevoll et al [26]. Scatter rate formulae for non-parabolic spherical band structure are well documented and we refer the reader to Fawcett et al [27].…”

“…Physical parameters of GaAs used in analytical Monte Carlo hole simulation. Most of the values are from Fischetti[22] except for the hole acoustic deformation potential and optical phonon energy which are from Brudevoll et al[26] and the hole optical deformation potential given by 2(ω o /u l ) from Brennan and Hess[11].…”

Femtosecond spectroscopy of unipolar nanometer-scale high-field transport in GaAs

“…4(a). For room temperature transport, we observe a smooth saturation of the drift velocity to values up to 7 x 10 6 cm/s consistent with calculations 19,20 and time-of-flight measurements for low electric fields 21 . For the case of T L = 4 K, an abrupt saturation of the hole velocity at v D = 1.15 x 10 7 cm/s is found.…”

Femtosecond spectroscopy of unipolar nanometer-scale high-field transport of holes in Al0.08Ga0.92As

“…2͒. For room temperature transport, we observe a smooth saturation of the drift velocity to values up to 7 ϫ 10 6 cm/ s consistent with calculations 8,9 and time-of-flight measurements for low electric fields. Fitting these transient to the experimental observation, two important transport parameters may be extracted from the data: ͑i͒ the mean carrier drift velocity of the holes propagating through the diode and ͑ii͒ the temporal spread-out of the carrier ensemble passing the end of the probe layer 240 nm apart from the area of carrier injection.…”