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(a) Schematic diagram of the HEIWIP structure. The doping concentration of the GaN emitter is , while the GaN bottom contact is doped to . The AlGaN barrier is not intentionally doped. By design, the Al fraction of AlGaN is set to 0.026 in order to have wavelength threshold. (b) The band diagram showing the conduction band profile. The band offset determines the wavelength threshold.
(a) Spectral response of the detector measured at under different biases and the calculated free carrier response fitted with the experimental curve at . The sharp drop at is due to the reststrahlen in GaN. The broad peak in the region on the free carrier response is probably due to carbon impurities and/or nitrogen vacancies in the structure. (b) Response at based on transition of Si donors in GaN.
Current-voltage curves at different temperatures under dark condition and the background photocurrent at . The detector has a BLIP of , and this is lower than the expected BLIP temperature due to the response at .
(a) Spectral response measured at 20, 30, 60, and under bias. The response decreased in strength as the temperature increased beyond . (b) Comparison of calculated IR absorption by thick GaAs and GaN films.
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