The effects of hydrogenation in high-purity p-type GaAs grown by molecular beam epitaxy and metalorganic chemical vapor deposition have been investigated by low-temperature photoluminescence and Hall-effect measurements. Before hydrogenation, photoluminescence measurements showed the dominant acceptor in the original samples was C, while after hydrogenation, the concentration of electrically active C acceptors was significantly reduced and the samples were highly resistive. These electrical and spectroscopic results show that C acceptors in GaAs can be passivated by hydrogenation.
HgCdTe infrared photovoltaic detectors were fabricated on silicon substrates for the first time by using intermediate CdTe and GaAs epitaxial layers. No cracking or degradation was observed after thermal cycling these devices (cutoff wavelength of 5.5 μm and R0A as high as 200 Ω cm2 at 80 K). Secondary ion mass spectrometry and Auger data substantiate that a CdTe buffer layer can prevent Ga diffusion from the intermediate GaAs epitaxial layer from inadvertently converting the p-HgCdTe to n-type at growth temperatures as high as 500 °C.
We present experimental evidence that current gain cutoff frequency (ft) values equal to or greater than those achieved with high electron mobility transistors (HEMTs) and pseudomorphic HEMTs can also be achieved by ion-implanted GaAs and InGaAs metal-semiconductor field-effect transistors. These measured ft results clearly suggest that the average electron velocity under the gate is determined primarily by the high-field electron velocity rather than the low-field electron mobility. Hence, we conclude that the transport properties of the two-dimensional electron gas in HEMTs and pseudomorphic HEMTs do not make a significant contribution to the high-frequency and high-speed performance of these devices.
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