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Diamonds are thought to be excellent candidates of next-generation semiconductor materials for high power and high frequency devices. A two-dimensional hole gas in a hydrogen-terminated diamond shows promising properties for microwave power devices. However, high sheet resistance and low carrier mobility are still limiting factors for the performance improvement of hydrogen-terminated diamond field effect transistors. In this work, the carrier scattering mechanisms of a two-dimensional hole gas in a hydrogen-terminated diamond are studied. Surface roughness scattering and ionic impurity scattering are found to be the dominant scattering sources. Impurity scattering enhancement was found for the samples after a high-temperature Al2O3 deposition process. This work gives some insight into the carrier transport of hydrogen-terminated diamonds and should be helpful for the development of diamond field effect transistors. [ABSTRACT FROM AUTHOR]

This paper investigated the temperature effects on the RF performances of the epitaxial bilayer graphene field-effect transistors (EBG-FETs) on a SiC substrate over a temperature range of 25–200 °C under the atmospheric environment. The temperature dependence of the cutoff frequency f T and the maximum oscillation frequency f max of the EBG-FETs with an identical gate-length and different gate-widths were measured by small-signal measurement up to 40 GHz. The results show that EBG-FETs are capable of operating at high temperature up to 200 °C with workable amounts of thermally induced performance degradation. To gain further insight into the underlying physics of the device parameters affected by temperature, the small signal device parameter variations with ambient temperature are discussed. This work reveals the great potential of graphene in high temperature device applications. Small signal current gain h 21 versus frequency measured in a temperature range of 25–200 °C. And the schematic diagram of dual-gated EBG-FET structure on SiC substrate. In this work, epitaxial bilayer graphene field-effect transistors (EBG-FETs) are fabricated on SiC substrate. The RF performances of the EBG-FETs are studied over a temperature range of 25–200 °C under the atmospheric environment. The results show that EBG-FETs are capable of operating at high temperature up to 200 °C. To gain further insight into the underlying physics of the device parameters affected by temperature, the small signal device parameter variations with ambient temperature are discussed. This work reveals the great potential for graphene in high temperature device applications. Image 1 [ABSTRACT FROM AUTHOR]

AlGaN/GaN polarization-doped field-effect transistors (PolFETs) were fabricated on the graded AlGaN/GaN heterojunctions grown by metal organic chemical vapor deposition, and the trap behaviors were first systemically evaluated by frequency-dependent conductance–voltage characterizations. It was found that there was no obvious effective traps accumulation in the graded AlGaN/GaN heterojunctions of the PolFETs due to the absence of abrupt heterostructure as in the traditional HFETs. The exactly exponential dependence of the trap state time constants on the bias voltage in PolFETs was observed, which was a typical characteristic for interface traps, indicating a multi-heterointerface feature of the PolFETs. [ABSTRACT FROM AUTHOR]