METAL CONTACTS TO GALLIUM-ARSENIDE

In this paper, some aspects that determine the properties of Schottky and ohmic contacts to GaAs are discussed. For Schottky barrier diodes (SBD), we present results of a comprehensive study involving 41 differ ent metals. We pay special attention to Ru and show that its thermal a nd chemical stability makes it ideal for use in devices operating abov e room temperature and for experiments involving annealing. Further, w e discuss the effect of different metallization methods on SBD propert ies and show that methods which use energetic particles, such as elect ron beam deposition and sputter deposition, often result in inferior S BD properties-the consequence of electrically active defects introduce d by the energetic particles at and close to the semiconductor surface . The advantages of using Ru as contact material to GaAs are that it f orms high quality, thermally stable Schottky contacts to n-GaAs and th ermally stable ohmic contacts with low specific contact resistance to p-GaAs. The versatile applicability of Ru contacts makes them extremel y important for future use in devices such as heterojunction bipolar t ransistors and solid state lasers.