Electrical Characteristics of Schottky Contacts to p-Type (001) GaP: Understanding of Carrier Transport Mechanism

Abstract

Formation of low-resistance ohmic contacts to p-GaP is important for development of high-efficiency AlGaInP light-emitting diodes (LEDs), which emit light from red to yellow-green and have a wide variety of applications such as traffic light lamps, automobile tail lamps, and in biotherapy. The current flow behavior can be understood by investigating the effect of the Schottky barrier height (SBH; Phi(B)) on the work function of metals (Phi(M)). In this work, SBHs and their dependence on Phi(M) at (001) p-GaP surfaces were investigated. With increasing temperature, the SBH increased, while the ideality factor decreased. This behavior is explained by means of a thermionic field-emission (TFE) model. The SBH and ideal factor ranged from 0.805 eV to 0.852 eV and from 1.18 to 1.50, respectively, for different Schottky metals. The S-parameter (d Phi(B)/d Phi(M)) was estimated to be 0.025, with this approximately zero value implying that the surface Fermi level is virtually perfectly pinned at the surface states at similar to 0.85 eV above the valence-band edge.