A microfabricated electrontunneling accelerometer as a directional underwater acoustic sensor AIP Conf.A single-electron tunneling transistor has been directly coupled on-chip to a high electron mobility transistor. The high electron mobility transistor ͑HEMT͒ is used as an impedance matching circuit with a gain close to unity. The HEMT transformed the 1.4 M⍀ output impedance of the single electron tunneling ͑SET͒ transistor by two orders of magnitude down to 5 k⍀, increasing its bandwidth to 50 kHz. This circuit makes it possible to observe the motion of individual electrons at high frequencies. The requirements for the bandwidth in high frequency applications is discussed.

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Transport through an array of small ohmic contacts alloyed to the twodimensional electron gas of a GaAs/AlGaAs heterostructure Appl.

We demonstrate the operation of a surface emitting light emitting diode. The wavelength of the emitted light can be tuned with the applied voltage. The device is based on a p-GaAs and n-Ga1−xAlxAs heterojunction containing an inversion layer in the p side and, GaAs quantum wells in the n side, and, is referred to as HELLISH-II (hot electron light emitting and lasing in semiconductor heterojunction). The device utilizes hot electron longitudinal transport and, therefore, light emission is independent of the polarity of the applied voltage.

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