Electrical resistivity and band-gap shift of Si-doped GaN and metal-nonmetal transition in cubic GaN, InN and AlN systems

Abstract

The critical impurity concentration N c of the metal–nonmetal (MNM) transition for the cubic GaN, InN and AlN systems, is calculated using the following two different criteria: vanishing of the donor binding energy and the crossing point between the energies in the metallic and insulating phases. A dielectric function model with a Lorentz–Lorenz correction is used for the insulating phase. The InN presents an order of magnitude increase in N c as compared to the other two systems. The electrical resistivity of the Si-donor system GaN is investigated theoretically and experimentally from room temperature down to 10 K. It presents a metallic character above a certain high impurity concentration identified as N c. The samples were grown by plasma assisted molecular beam epitaxy (MBE) on GaAs (0 0 1) substrate. The model calculation is carried out from a recently proposed generalized Drude approach (GDA) presenting a very good estimation for the metallic region. The band-gap shift (BGS) of Si-doped GaN has also been investigated above the MNM transition where this shift is observed. Theoretical and experimental results have a rough agreement in a range of impurity concentration of interest.