Chern I Huang

US Patent:

57341931, Mar 31, 1998

Filed:

Aug 30, 1995

Appl. No.:

8/521513

Inventors:

Burhan Bayraktaroglu - Huber Heights OH
Lee L. Liou - Dayton OH
Chern I. Huang - Beavercreek OH

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

H01L 29201
H01L 27082
H01L 2334

US Classification:

257579

Abstract:

Structure and fabrication details are disclosed for AlGaAs/GaAs microwave HBTs having improved thermal stability during high power operation. The use of a thermal shunt joining emitter contacts of a multi-emitter HBT is shown to improve this thermal stability and eliminate "current-crush" effects. A significant reduction in thermal resistance of the disclosed devices is also achieved by spreading the generated heat over a large substrate area using thermal lens techniques in the thermal shunt. These improvements achieve thermally stable operation of AlGaAs/GaAs HBTs up to their electronic limitations. A power density of 10 mW/. mu. m2 of emitter area is achieved with 0. 6 W CW output power and 60% power-added efficiency at 10 GHz. The thermal stabilization technique is applicable to other bipolar transistors including silicon, germanium, and indium phosphide devices. The disclosed fabrication sequence employs an improved two-step polyimide electrical isolation planarization sequence in preparation for fabrication of the thermal shunting element.

US Patent:

54951801, Feb 27, 1996

Filed:

Feb 4, 1994

Appl. No.:

8/194997

Inventors:

Chern I. Huang - Beavercreek OH
Mark Calcatera - Spring Valley OH

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

G01R 2726
G01R 3128
H01P 1162

US Classification:

324765

Abstract:

A small sized energy conveying and signal dissipating loading apparatus for use in the testing of a transistor of the high gain high frequency type is disclosed. The energy conveying and loading device of the invention employs a transmission line-like network of distributed components in order to roll off and dampen or dissipate the high frequency alternating current response of the transistor under test while also being electrically invisible for measuring the low frequency or DC characteristics of the transistor under test. The described energy communicating and loading apparatus is compatible with the temperatures of a test environment for even the most extreme environment transistor devices and allows convenient placement in the test environment immediately adjacent the transistor under test. The load allows testing of multiple transistor devices with reasonable space and cost requirements. Use of the energy communicating and loading invention with a hetrojunction bipolar transistor of the microwave type and in conjunction with discrete bypass capacitors are also disclosed.