Thermal degradation of polished InP surfaces of (001) and (111) B orientations has been investigated. These specimens show severe deterioration when annealed under conditions typically used in the LPE growth of InP and InGaAsP layers. We have successfully controlled the decomposition of InP substrates in LPE growth by introducing minute amounts of phosphine gas (PH3) into the flowing hydrogen ambient. A temperature-dependent threshold concentration has been determined above which no thermal degradation is observed.
SIRTF requires detector arrays with extremely high sensitivity, limited only by the background irradiance. Especially critical is the near infrared spectral region around 3 µm, where the detector current due to the zodiacal background is a minimum. IRAC has two near infrared detector channels centered at 3.6 and 4.5 µm. We have developed InSb arrays for these channels that operate with dark currents of <0.2 e -/s and multiply-sampled noise of ~7 e -at 200s exposure. With these specifications the zodiacal background limited requirement has been easily met. In addition, the detective quantum efficiency (DQE) of the InSb devices exceeds 90% over the IRAC wavelength range, they are radiation hard, and they exhibit excellent photometric accuracy and stability. Residual images have been minimized. The Raytheon 256 x 256 InSb arrays incorporate a specially developed (for SIRTF) multiplexer and high-grade InSb material.
Photoluminescence measurements on Si-doped GaAs single crystals heat treated in vacuum at 400≲T≲800 °C reveal emission peaks at 1.363, 1.409, and 1.487 eV, which correspond to three acceptor levels introduced through the activation of vacancies and the site transfer of Si atoms during the annealing process.
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