[19p-F202-1~16] 13.2 Exploratory Materials, Physical Properties, Devices

[19p-F202-3] Analysis of impurity conduction in n-type GaAs based on a Hubbard-band model

〇Yasutomo Kajikawa¹ (1.Shimane Univ.)

Keywords:hopping conduction, Hall effect

The low-temperature data of Hall-effect measurements on weakly compensated n-GaAs samples with donor concentrations N_D less than the critical concentration for the metal-insulator transition reported in literature have been analyzed on the basis of a Hubbard-band model, which includes not only the bottom Hubbard band formed from the neutral donor (D⁰) states but also the top Hubbard band formed from the negatively charged donor (D^-) states. In the model, the drift mobility and the Hall factor of nearest-neighbor hopping (NNH) in the top Hubbard band are assumed to be expressed as μ₂ = μ₀₂(E₂/k_BT)^3/2exp(-E₂/k_BT) and A_H2 = (k_BT/J_H2)exp(K_H2E₂/k_BT), respectively, according to the small-polaron model, while those of variable-range hopping (VRH) in the bottom Hubbard band are assumed to be expressed as μ₃ = μ₀₃(T_ES/T)^1/2exp[-(T_ES/T)^1/2] and A_H3 = A_H03(T_ES/T)^1/2exp[(1 - ν) (T_ES/T)^1/2] according to the Efros-Shklovskii (ES) model. For the sample with a donor concentration of N_D = 1.3 ×10¹⁵cm^-3 and a compensation ratio of K = 0.27, it is shown that the Hall mobility is dominated by NNH in the top Hubbard band in a temperature range of 3.5-15 K while it is dominated by ES VRH in the bottom Hubbard band below 3.3 K.