Irradiation 2004/11/08

People: Iwaida, Stanic, Yoda

Irradiated samples: REM RadFET TOT500, NEC 2SJ209, NEC 2SJ461

Dose: 600kRad at 109kRad/h

All samples were p-MOSFET transistors. We measured the
Id vs. Ug characteristic of the transistor as a function
of dose. The gates and the drains of the transistors
were not shorted.

During irradiation, the G D S of the transistors were shorted.
Experiment proceeded in a series of irradiations to
100, 200, 400 and 600kRad, after each irradiation the characteristic
of the transistor was measured.

During the measurement, D was connected to -10.6V, while S was
grounded. Drain current Id was then measured as a function of
variable Ug, which was changeable in the range [0,24V].

TOT500 RadFET were known to have a temperature independent point
at 160uA, but as we did not know the total current applicable,
we measured the characteristic to 4000uA only. We could see
clear horizontal shift of the curve without any change in its
inclination.

2SJ209 and 2SJ461 were rated to withstand 100mA, so we measured the
characteristic curve up to the saturation, which was reached at 80mA and
100mA respectively. The shift of the characteristic was in both cases
linear translation only, however, 2SJ209 seems more suitable for dosimetry
as its threshold gate voltage shows nicer dependence vs. accumulated dose.

For 2SJ209 and 2SJ461 temperature independent value of drain current
still remains to be found in order for them to be used for dosimetry
purposes.