Characterization of Pd/Sn ohmic contacts on n-GaAs using electrical measurements, EDAX and SIMS

Abstract

A non-alloyed Pd/Sn ohmic contact on n-GaAs has been developed. Metallization samples are: annealed at various temperatures and systematically characterized using Energy Dispersive Analysis of X-rays (EDAX), Secondary Ion Mass Spectrometry (SIMS) and current-voltage (I-V) measurements. Contact resistivities, /spl rho//sub c/, of the proposed metallization are measured utilizing a transmission line model (TLM) method. Annealing at 360/spl deg/C for 30 min yielded the lowest /spl rho//sub c/ of /spl sim/3.26/spl times/10/sup -5/ /spl Omega/-cm/sup 2/ on 2/spl times/10/sup 13/ cm/sup -3/ n-GaAs with a Pd(300 /spl Aring/)/Sn(1500 /spl Aring/) contact. The EDAX spectra show a correlation between Ga signal peaks and measured /spl rho//sub c/ values at various annealing temperatures. The contact depth profiles are analyzed by SIMS. The effect of metallization thickness on contact properties are also presented. The mass spectrometer analysis confirms the formation of PdGa and SnGa compounds at the lowest /spl rho//sub c/ condition.