Forward-bias characteristics of Si bipolar junctions grown by molecular beam epitaxy at low temperatures

Abstract

Forward-bias current-voltage characteristics of molecular beam epitaxy grown Si p+-i-n+ junctions have been determined at room temperature. At small widths of the i zone (Li=5 and 10 nm) band-to-band tunneling with a maximum peak-to-valley ratio of two is observed. Up to Li=30 nm (trap assisted) forward-bias tunneling is apparent with saturation tunneling current densities somewhat lower than in p-n junctions at comparable widths of the space-charge region WSCR(0). For Li≳30 nm and Tg=500 °C growth temperature surface recombination dominates the low bias range. At Li=35 nm and Tg=325 °C, both surface and bulk recombination is observed. We found evidence that Si molecular beam epitaxy layers grown at this low temperature get an increasing density of crystalline defects with growing thickness.