ELECTRONIC STABILITY OF THE REACTIVELY SPUTTERED HYDROGENATED AMORPHOUS-SILICON THIN-FILMS - THE EFFECT OF HYDROGEN CONTENT

The total hydrogen content (CH) of reactively sputtered hydrogenated amorphous silicon (a Si:H) films can be independently controlled by adjusting the partial pressure of hydrogen (PH2) during deposition. We report on the electronic stability of direct-current (dc) magnetron reactive sputtered films deposited at a constant substrate temperature of 230 °C with various. PH2. The films have CHfrom — 13 to 28 at. % and similar, device quality properties in the as deposited state. The photoconductivities of all the films are between 0.9 to 3X10−5 (Ω cm)−1 under AM-1 (air mass- 1)illumination (100 rnW/cm2). The density of deep states (DOS) measured by the constant photocurrent method is ∽ 6x1015 cm−3 for low CH (≤15 at. %) and ~2x1015 cm 3 for high CH(≥17) films. Light induced degradation measurements show a systematic correlation between CHand the electronic stability; the low CH films have a slower rate of photoconductivity decrease, and slower DOS increase, than either the high CHfilms or one glow-discharge deposited film tested for comparison. In fact the low CH a Si:H appears superior after just a few hours of light exposure. © 1990, American Vacuum Society. All rights reserved.