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The authors report on the fabrication and characterization of thin film transistors that use sputter deposited amorphous indium zinc oxide both for the channel and source-drain metallizations in a gate-down configuration. The channel and source-drain layers were deposited from a single In2O3–10 wt %ZnO ceramic target using dc magnetron sputtering onto an unheated substrate. The carrier densities in the channel (2.1×1017/cm3) and source/drain regions (3.3×1020/cm3) were adjusted by changing the reactive oxygen content in the sputter chamber during deposition. The resulting transistors operate as depletion mode n-channel field effect devices with saturation mobility of 20 cm2/V s and on/off current ratio of 108. [ABSTRACT FROM AUTHOR]

Polytype heterostructures of GaSb/AlSb/InAs show interband tunneling due to the 0.1 eV overlap of the InAs conduction band and the GaSb valence band. This broken-gap configuration results in a novel mechanism for negative differential resistance that has potential applications in high-speed devices. We have demonstrated for the first time interband tunneling in single-barrier and double-barrier polytype heterostructures. Single-barrier structures show negative differential resistance due to the change in interband tunneling with applied bias. A peak-to-valley ratio of 2.7:1 at 77 K was observed in this case. Double-barrier structures using an InAs quantum well exhibit resonant interband tunneling with a peak-to-valley current ratio of more than 60:1 at 77 K. This structure is promising for applications to three-terminal devices because of the very wide quantum well that can be achieved. [ABSTRACT FROM AUTHOR]

Clear negative differential resistance has been observed in a GaAs/AlAs/GaAs single-barrier heterostructure due to the presence of a quasi-bound state associated with the X-point profile. This surprising result is due to the fact that although the Γ-point profile of this heterostructure is a simple single tunneling barrier, the X-point profile actually constitutes a quantum well some 0.3 eV deep lying about 0.2 eV above the Γ point of GaAs. The experimental evidence is a sharp cutoff in conductance at about 0.36 V bias, characteristic of tunneling via a confined state. [ABSTRACT FROM AUTHOR]

We have fabricated the first InAs-channel field-effect transistor, which shows a transconductance of 180 mS/mm at 1 V drain-source bias (77 K). An improved buffer layer could significantly improve the device performance. In addition, we propose a new broken-gap heterojunction field-effect transistor based on these materials that could provide an order of magnitude higher transconductance compared to existing device configurations based on AlGaAs/GaAs. [ABSTRACT FROM AUTHOR]

AlAs/GaAs/AlAs double-barrier heterostructures grown along the (111) crystal axis show a factor of two improvement in the peak-to-valley ratio compared to samples grown in the (100) orientation. A structure consisting of 2.8 nm barriers and an 8 nm well shows a peak-to-valley ratio much better than any published results on (100) oriented structures with similar well and barrier layers. This result is interpreted in terms of the increased effective mass for carriers tunneling inelastically via the AlAs X-point barrier. An increased mass leads to a reduction in the barrier transmission probability and, therefore, a decrease in the leakage current due to inelastic tunneling. [ABSTRACT FROM AUTHOR]

We have observed for the first time negative differential resistance at room temperature in a single-barrier tunneling heterostructure. A typical InAs/AlGaSb/InAs structure exhibits a current peak of 2.1×103 A cm-2 at 0.28 V and a peak to valley ratio of 1.6:1. We attribute the observation of room-temperature negative differential resistance to the favorable band alignment in the AlGaSb/InAs material system, which appears promising for device applications of single-barrier tunneling. [ABSTRACT FROM AUTHOR]

We report the first observations of resonant tunneling in the AlSb/InAs material system, with a maximum peak-to-valley current ratio of 1.8:1 at room temperature and 9:1 at 77 K. The large AlSb/InAs barrier height of 1.8 eV for electrons and high-mobility InAs will be advantageous in device applications. In particular, the small electron effective mass in InAs makes it possible to demonstrate quantum effects in a 24 nm well, the longest coherence distance reported for double-barrier tunneling structures. We estimate that an AlSb/InAs resonant tunneling transistor can significantly outperform similar devices based on AlGaAs/GaAs. [ABSTRACT FROM AUTHOR]