Highly stable W/p-In0.53Ga0.47As ohmic contacts formed by rapid thermal processing

Tungsten contacts to Zn-doped In0.53Ga0.47As have been formed by rapid thermal processing. Contacts to layers with a Zn doping concentration of 5×1018 cm−3 were rectifying as sputter deposited as well as after heat treatments at temperatures lower than 450 °C. Higher processing temperatures caused a linear decrease of the contact resistivity values from 0.6 as deposited to 0.15 Ω mm after heating at 550 °C. Rapid thermal processing at these higher temperatures stimulated the Schottky-to-ohmic contact conversion with a minimum contact resistance value of 8.5×10−5 Ω cm2 and a sheet resistance value of 150 Ω/⧠ as a result of heating at 600 °C for 30 s. By increasing the p-InGaAs doping level to 1×1019 cm−3, the specific resistance of this contact was dropped to the minimum of 7.5×10−6 Ω cm2 as a result of heating at 600 °C for 30 s. The W/p-In0.53Ga0.47As contact showed excellent thermal stability over the temperature range of 300–750 °C, with an abrupt and almost unreacted metal-semiconductor interface. Heating at temperatures of 800 °C or higher caused degradation of the contact. This was reflected by a distinct increase in the heterostructure sheet resistance as a result of the intensive interfacial reaction which took place at the contact, accompanied by outdiffusion of both In and As.