Properties of nanometer-sized metal-semiconductor interfaces of GaAs and InP formed by an in situ electrochemical process

The properties of GaAs and InP Schottky diodes having nanometer-sized metal dots were investigated in order to clarify whether or not strong Fermi lev el pinning is an intrinsic property of the metal-semiconductor interface. M acroscopic Schottky diode samples having many nanometer-sized metal dots as well as single-dot Schottky diode samples were prepared by an in situ elec trochemical process which consisted of pulsed anodic etching of the semicon ductors followed by subsequent de or pulsed cathodic deposition of the meta l. Strong Fermi level pinning was not seen in the GaAs and InP macroscopic samples. The Schottky barrier height SBH values were strongly dependent on the metal work function and on the electrochemical processing conditions. O f particular interest, the difference in the dot size changed the SBH almos t 340 meV in Pt/InP macroscopic Schottky diodes, indicating that Fermi leve l pinning disappears as the dot size is sufficiently reduced. X-ray photoel ectron spectroscopy and Raman measurements indicated that these interfaces are oxide and stress free. Use of an atomic force microscope with a conduct ive probe allowed direct I-V measurements on single-dot samples. The metal work function and dot size dependencies of the SBHs in these samples were s imilar to those in macroscopic samples. Large ideality factors observed in the single-dot sample were explained in terms of environmental Fermi level pinning which produces a saddle point potential. The metal work function de pendence of the SBHs measured as well as the relationship between the SBH a nd the ideality factor were both far from what was found in recent predicti ons based on the metal-induced gap state model. All the experimental result s were consistently explained by the disorder-induced gap state model which asserts that strong Fermi level pinning is an extrinsic property of the me tal-semiconductor interface. (C) 1999 American Vacuum Society. [S0734-211X( 99)04704-6].