Abstract
The objective of thisresearch was to develop ohmic contact schemes of low resistance, i.e. in the mid10-1 QCM2, to p-type Gallium Phosphide by the mechanism of solid-phase regrowth. The contact resistivityof the samples fabricated in this work was measured by the Cox-Strack method. Ohmic contacts based on the Zn/Pd system were developed. The Zn(350A)/Pd(IOOA)/p-GaP and Zn(350A)/Pd(IOOA)/p-GaP gave rather high values of the contact resistivity, 3-8xl 0-4 f2CM2. An improvement in the contact resistivity was achieved by developing the Si(750A)/Pd(400A)/Zn(xA)/Pd(IOOA)/p-GaP scheme. Values of the contact resistivity in the range of 3xlO-5 to 7xlO-' nCM2 were obtained. It was found that the optimum Zn layer thickness is 30 A for the Pd and Si thickness used in this scheme. The samples were annealed for I @n at temperatures ranging from 3 5 0 to 4 5 0 'C. Lower values of the contact resistivity than those of the Si/Pd/Zn/Pd/p-GaP scheme were achieved by depositing an Aluminum layer on the top of the Si/Pd/Zn/Pd/p-GaP system. Values of the contact resistivity in the range of 2xl 0-5 f2CM2 to 5xlO-5 flcM2 were achieved for the contacts AI(IOOOA)/Si(750A)/Pd(400A)/Zn(30A)/Pd(IOOA)/p-GaPand AI(200A)/Si(750A)/Pd(400A)/Zn(30A)/Pd(IOOA)/p-GaP, respectively. The low values of the contact resistivity were attributed to the formation of a heavilydoped surface layer beneath the contact area. The doping concentration of this surface layer was estimated by using theoretical plots of the contact resisvity versus doping concentration.
Jorge Estevez, Humberto Angel (1996). Ohmic contacts to p-type GaP. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -J675.