Depth profiles of H, C, O, Al and Si implants in a GaN substrate using trace element accelerator mass spectrometry

Abstract

The compound semiconductor GaN has become the electronic material for many semiconductor applications because of its high-power, high-temperature and high-frequency characteristics. The introduction of impurities to GaN, either by direct doping or by contamination of unwanted impurities during fabrication leads to changes in its electronic properties [CAARI 2002: 17th International Conference on the Application of Accelerators in Research and Industry, American Institute of Physics, Vol. 680, 2002, p. 369]. There are a number of techniques routinely used to analyze the depth profiles of impurities in semiconductor substrates, but they lack the sensitivity required for today's applications. For example, secondary ion mass spectrometry (SIMS) has molecular interferences which obscure analysis of some elements. Trace element accelerator mass spectrometry (TEAMS), which is a combination of accelerator mass spectrometry (AMS) and SIMS, removes molecular interferences by breaking apart the molecules in an accelerator. Like SIMS, secondary ions are sputtered from a target, the negative ions are then extracted and injected into a 3 MV tandem accelerator. As they pass through a gas at the center of the terminal, molecular breakup is achieved via a coulomb explosion due to electron stripping. The ions are then passed through momentum/charge and energy/charge filters, which are used to separate out many of the unwanted interferences. In most cases, TEAMS is a complimentary technique to SIMS and can eliminate the interferences that may not be resolvable by SIMS. The purpose of this work is to examine the depth profiles and detection limits of various impurities implanted into a GaN substrate.