Abstract
We present the cofabrication of planar Gunn diodes and high-electron mobility transistors (HEMTs) on an indium phosphide substrate for the first time. Electron beam lithography has been used extensively for the complete fabrication procedure and a 70-nm T-gate technology was incorporated for the enhancement of the small-signal characteristics of the HEMT. Diodes with anode-to-cathode separation (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ac</sub> ) down to 1and 120-μm width were shown to oscillate up to 204 GHz. The transistor presents a cutoff frequency ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) of 220 GHz, with power gain up to 330 GHz ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ). The integration of the two devices creates the potential for the realization of high-power, high-frequency MMIC Gunn oscillators, circuits, and systems.
Highlights
T HE Gunn diode oscillator was discovered in 1963 [1], while Gunn was examining the current–voltage characteristics of GaAs and indium phosphide (InP)
We demonstrate the cofabrication of planar Gunn diodes and high-electron mobility transistors (HEMTs) on the same InP substrate for the first time
The measurements correspond to HEMTs with two-finger 70-nm T-gates and 25-μm width
Summary
T HE Gunn diode oscillator was discovered in 1963 [1], while Gunn was examining the current–voltage characteristics of GaAs and indium phosphide (InP). The first planar Gunn diodes operating above 100 GHz were presented recently, where Lac was selected accurately through the lithographic design [7]. Using this method, signals at different frequencies can be generated from diodes with different geometries, implemented on the same chip. The implementation of planar Gunn diodes and pHEMTs on GaAs substrates side-by-side has been recently studied [11], demonstrating the potential for amplification of the diode signal using a transistor-based amplifier on the same IC. Planar devices with a single channel layer of In0.53Ga0.47As grown on InP have demonstrated exceptional characteristics with 164-GHz maximum frequency of oscillation and −10-dBm generated power [12]. The fabrication process of the Gunn diode is described in detail, presenting the required compatibility with the HEMT material system
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