ELECTRICAL AND OPTICAL CHARACTERIZATION OF METAL/N-INP INTERFACES FORMED BY A CRYOGENIC PROCESS IN HIGH-VACUUM

We report a novel low temperature (LT = 77 K) deposition process at high vacuum to make reliable, high-barrier height Schottky contacts to n-InP. The electrical and interface properties of the metal/n-InP were investigated by current-voltage (I-V) and capacitance (C-V) techniques, photoreflectance (PR), and Raman spectroscopies. For the LT diode made on Sn-doped n-InP, the leakage current density J0, and barrier height phi(B) wer found to be 1.4X10(-8) A/cm2 and 0.83 eV, respectively. Undoped InP gave J0 = 6.7X10(-11) A/cm2 and phi(B) = 0.96 eV. This indicated a reduction of more than six orders of magnitude in J0, corresponding to a 0.4-0.5 eV increase in phi(B) compared with the metal/n-InP diodes made at room temperature (RT = 300 K). The Schottky metal property was studied as a function of deposition temperature and film thickness. Very good agreement was obtained between the electrical and the optical measurements. The high barrier height and low leakage current can be attributed to the dual modification of metal and InP near the interface as well as less disruption of the InP surface.