Study on the effect of high magnetic field on electron transport in lattice mismatched n-GaN grown on sapphire based on two-layer model

GaN for its wide band gap has gained popularity for its use in semiconductor devices. To this date there have been no successful techniques devised for production of bulk GaN of technologically suitable size. The mostly closed lattice matched substrate of reasonable cost is sapphire. SiC is more closely matched but it is very costly. Due to lattice mismatch, large number of dislocations develop near the interface which reduces sharply in the bulk layer. So the bulk n-GaN may be considered to be consisting of two layers, one being the thin interfacial layer where dislocations are very high. The layer above the interfacial layer just above the substrate is another layer, the bulk layer where the dislocation is less and negligible. With two layers in consideration, we have calculated the various transport parameters such as mobility, Seebeck coefficient and conductivity under the extreme quantum limit. In our model, the dislocation scattering and the ionized impurity scattering mechanisms are considered in the interfacial layer and in the bulk layer other scattering mechanisms like the acoustic phonons via deformation potential and the piezoelectric potential, the ionized impurity scattering and the polar optical phonon scattering are considered. We have studied the transport parameters at high and low temperatures. For studies in the low temperatures, the polar optical phonon scattering is not considered. The study shows that combined conductivity decreases with increase in magnetic field at high temperatures whereas it increases at low temperatures. At all the situations the dislocation scattering affects the combined conductivity and the thermoelectric power of GaN and lowers the value of transport parameters. (C) 2008 Elsevier B.V. All rights reserved.