CONDUCTION MECHANISMS IN ORDERED GAINP2 EPILAYERS

A Hall-Van der Pauw and high-field magnetotransport study is reported on GaInP2 epilayers, which contain naturally ordered regions with lower band gap than that of the embedding disordered regions. Below T=200 K three conductivity mechanisms are distinguished in this material: hopping conduction with activation energy epsilon3 dominates for T < 30 K, band conduction with activation energy epsilon1 for T > 85 K, and epsilon2 conduction at intermediate temperatures with activation energy epsilon2. The behavior of the conductivity sigma in a transverse magnetic field B is found to be in good agreement with theory. The activation energy epsilon2 shows excellent quadratic dependence on B, and the preexponential factor sigma3 is proportional to exp(-constB0.54+/-0.04). Mobility data above T=200 K show unprecedented proof of cluster scattering: calculations based on the Harrison-Hauser/Marsh formalism revealed cluster radii of 3.5 nm and provided absolute values for the fractions of the crystal volume occupied by ordered clusters.