LOW-TEMPERATURE ELECTRICAL SURFACE PASSIVATION OF MBE-GROWN PIN DIODES BY HYDROGEN AND OXYGEN PLASMA PROCESSES

The electrical surface passivation of mesa-shaped pin diodes was inves tigated by three different processes: (1) wet thermal oxidation at 700 degrees C, (2) plasma enhanced oxidation at 360 degrees C, (3) plasma enhanced hydrogenation at room temperature. With the plasma-assisted low-temperature processes (2) and (3) low values of leakage currents w ere achieved compared with the reference process (1), whereas after re moval of the oxide passivation layer by HF and subsequent water rinsin g the leakage current was significantly higher. According to our model , current transport is supported by mobile charges at the Si surface w hich are mainly present after process (2) and after removal of the the rmal oxide passivation layer by HF. The plasma hydrogen termination of the Si surface lasts for several days since buried hydrogen serves as a reservoir against the decay of Si-H-x surface sites by desorption. (C) 1998 Elsevier Science S.A. All rights reserved.