Spectral and Spatial Response of Sulfur-Hyperdoped n+/p Silicon Photodiodes*

Pulsed laser melting of implanted silicon can enable doping well above equilibrium concentrations. Sulfur doping leads to a deep donor state that may form an impurity band at high enough concentrations. Photodiodes formed from sulfur-hyperdoped n+ layers on a p-type wafer have shown external quantum efficiency of much greater than 100\%, as well as enhanced infrared response. In this paper we report on optoelectronic characterization of diodes prepared by implantation of 10$^{15}-10^{16}$ sulfur/cm2 into a p-type wafer, followed by nanosecond pulsed laser melting and recrystallization. Experimental results from wavelength-dependent diode response, spatial quantum efficiency mapping, intensity dependent efficiency, and current-voltage techniques will be reported. We will also discuss potential models for the observed behavior.