THE LIMITED SPACE-CHARGE ACCUMULATION MODE IN BULK GALLIUM ARSENIDE.
Interim technical rept.,
CORNELL UNIV ITHACA NY SCHOOL OF ELECTRICAL ENGINEERING
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The limited space-charge accumulation LSA mode provides a source of microwave power at the circuit frequency by inhibiting the formation of high field domains. LSA operation is possible when the GaAs device is placed in a high Q anti-resonant circuit, and the ratio of carrier density to circuit frequency nf is between 10,000 and 200,000 seccc. The optimum nf ratio for space-charge control was determined experimentally at S-band for several different bias fields. The nf ratio for highest efficiency was found to increase with the applied field. The variation of efficiency with the microwave resistance at the device terminals was also investigated. For a device biased at three times the threshold field for traveling domains, the peak efficiency was obtained when the circuit resistance was 12-13 times the low field resistance of the sample. The results agree very well with computer simulations of the LSA mode based on Butcher and Fawcetts velocity-field characteristic. Peak powers of 88 watts at S-band for 0.4 microsec pulses were obtained with a device operated at eight times the domain threshold.
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