Long Time Relaxation Process in MOSFET Devices

• Published in: Japanese Journal of Applied Physics 1987-01, Vol.26 (S3-2), p.1695
• Main Authors: Porjesz, Tamás, Kovács, György, Kirschner, István, Kármán, Tamás, Zsolt, Gábor
• Format: Article
• Language: English
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAPS.26S3.1695

Transistor characteristics in implanted MOSFET structures were measured up to higher drain voltages. Applying a drain voltage above a critical value we observed a decreasing drain current at constant drain and gate voltages. The decrease of the current has shown an exponential-like behaviour having a time constant of 15 minutes. After swithching off the drain voltage the current, or better to say, the conductivity started to increase with a time constant somewhat higher than the decreasing one. The critical drain voltage depends on the temperature and on the gate voltage as well. At room temperature the critical voltage in the range of 30 volts while at helium temperatures it is in the range of 10 volts. For all of the measurements a gate voltage near the threshold was used to avoid the sample heating by the higher drain current. The effect could be explained by slowly depleting and filling traps in the insulating layer. The measurements gave similar results for n- and p-channel insulated gate MOSFET-s.