High-dose oxygen ion implanted heterointerfaces in silicon

Emitter-base band gap differentials realized with alloys such as Si_xGe_1-x, SiC_x and μc-Si:H have been widely investigated for stretching the performance of Si bipolar transistors. We report on the properties of wide-gap surface regions generated in crystalline Si (c-Si) by high-dose oxygen ion implantation. The electrical and physical property changes of crystalline Si after substoichiometric O ion implantation have been investigated using current-voltage, capacitance-voltage, spreading resistance, secondary ion mass spectroscopy, spectroscopic ellipsometry and Fourier transform infrared spectroscopy. A key finding is the presence of donors in the vicinity of the implanted region, resulting in extensive counterdoping of p-type c-Si. Redistribution of the oxygen atoms during the high-temperature (1200°C) anneal results in sharp interfaces aiding the formation of the heterojunction. Mesa-type diodes on the implanted sample exhibit excellent rectification with diode ideality factor of 1.2, and a room temperature reverse saturation current density of 1 × 10^-8 A/cm² with a thermal activation energy of 0.92 eV.