USA As Represented by Secretary of the Navy

J Brad Boos

Walter Kruppa

Brian R Bennett

Doewon Park

Ming-Jey Yang

Galina Kelner

Kiki Ikossi-Anastasiou

Steve C Binari

Heterostructure field-effect transistors (HFETs) and other electronic devs are fabricated from a series of semiconductor layers to have reduced impact ionization. On to a first barrier layer there is added a unique second subchannel layer having high quality transport properties for reducing impact ionization. A third barrier layer having a controlled thickness to permit electrons to tunnel through the layer to the subchannel layer is added as a spacer for the fourth main channel layer. A fifth multilayer composite barrier layer is added which has at least a barrier layer in contact with the fourth channel layer and on top a sixth cap layer is applied. The device is completed by adding two ohmic contacts in a spaced apart relationship on the sixth cap layer with a Schottky gate between them which is formed in contact with the fifth barrier layer. The second subchannel layer and the fourth main channel layers are made of materials which have the proper respective energy gaps and ground state energies such that during use the transfer of hot electrons from the main channel into the subchannel is made probable to reduce impact ionization in the main channel. In the preferred AlSb/InAs-based HFETs, the use of an Is InAs subchannel layer under the main InAs channel improves the performance of the HEMTs particularly for gate lengths in the deep-submicron regime. The devices exhibit higher transconductance, lower output conductance, reduced gate leakage current, higher operating drain voltage, and improved frequency performance.

Channel design to reduce impact ionization in heterostructure

The use of lactic acid or its derivative in compositions to etch or polish materials containing indium phosphide results in treated surfaces that have reduced surface roughness compared to the surfaces treated with compositions devoid of lactic acid or its derivative. Indium phosphide surfaces treated with compositions containing lactic acid can have treated surfaces that are smooth or mirror-like, meaning that surface irregularities thereon are less than about 50 .ANG..

Lactic acid treatment of InP materials

A heterojunction device, and a method for producing the device. A gate air bridge is formed at the mesa sidewall between the active region and the gate bonding pad to lower the gate leakage current. The device has a double recessed gate to reduce local fields in the vicinity of the gate. The fabrication method uses dielectric intermediate and final passivation layers to optimize the double-recess profile and control the extension of the high-field region between the gate and the drain. This combination increases the breakdown potential of the device, but minimizes the effective gate length of the device, preserving high frequency performance.

Fabrication method for III-V heterostructure field-effect transistors

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Springfield, VA, United States of America

J Brad Boos