News Column

Patent Issued for Monolithic HBT with Wide-Tuning Range Varactor

May 21, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- Global Communication Semiconductors, Inc. (Torrance, CA) has been issued patent number 8716757, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Yang, Yuefei (Torrance, CA); Wang, Shing-Kuo (Torrance, CA).

This patent was filed on October 31, 2012 and was published online on May 6, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "While the benefits of implementing virtually any electronic circuit on a single integrated circuit (IC) are well known, some electronic circuits are difficult to implement as a monolithic, single IC (sometimes called MMICs for monolithic microwave integrated circuits), because distinct elements of the circuit require properties that are not desirable in other elements. In the case of wide-band microwave-range voltage controlled oscillators (VCOs), the variable capacitor element (varactor) needs a high breakdown voltage to implement a wide tuning frequency range, and the high breakdown voltage typically requires a thick layer of the relevant material, which leads to a higher resistance in that layer than a thinner layer of the same material. While that is not an issue in the varactor, using the same set of material layers for the transistor element of a VCO would result in unsatisfactory transistor performance, due to the relatively longer transit time in the collector. As a result, wide-band microwave frequency VCOs are typically not implemented as MMICs."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "A semiconductor device has tunable capacitance that varies in accordance with a voltage applied between a first contact and a second contact. The semiconductor device comprises a substrate, a semiconductor base layer comprising a first semiconductor material having a first band-gap, and a plurality of successive semiconductor layers positioned between the substrate and the semiconductor base layer. The plurality of successive semiconductor layers includes a tuning layer comprising a second semiconductor material having a second band-gap larger than the first band-gap. The tuning layer also has a non-uniform doping profile with a doping concentration that varies in accordance with the distance from the surface of the tuning layer proximal to the semiconductor base layer. The first contact is electrically coupled to the semiconductor base layer and the second contact is electrically coupled to a respective layer in the plurality of successive semiconductor layers.

"In some embodiments, the device comprises a heterojunction bipolar transistor (HBT) having a base, collector and emitter. The semiconductor base layer comprises the base of the HBT. At least one respective layer of the plurality of successive semiconductor layers comprises the collector of the HBT. The device further comprises one or more additional semiconductor layers that comprise the emitter of the HBT. At least one of the additional semiconductor layers comprises a third semiconductor material having a third band-gap.

"In some embodiments, the HBT is a double heterojunction bipolar transistor, and the first band-gap (e.g., the band-gap corresponding to the semiconductor base layer), is smaller than the second band-gap and the third band gap. In some embodiments, the HBT is a single heterojunction bipolar transistor, and the first band-gap and the third band-gap are the same or nearly the same.

"In some embodiments, the device comprises a voltage controlled oscillator that includes an HBT and at least one additional circuit element. The HBT includes the substrate, a semiconductor base layer, plurality of successive semiconductor layers positioned between the substrate and the semiconductor base layer, the first contact and the second contact.

"In some embodiments, the device comprises a voltage controlled oscillator that includes a varactor and at least one additional circuit element. The varactor includes the substrate, a semiconductor base layer, plurality of successive semiconductor layers positioned between the substrate and the semiconductor base layer, the first contact and the second contact.

"In some embodiments, at least one of the semiconductor substrate and a respective layer of the plurality of successive semiconductor layers, excluding the tuning layer, comprises gallium arsenide (GaAs).

"In some embodiments, the tuning layer comprises an indium gallium phosphide (InGaP) layer.

"In some embodiments, the non-uniform doping profile of the tuning layer comprises a graded doping profile that monotonically decreases from the surface of the tuning layer proximal to the semiconductor base layer to an opposing surface of the tuning layer distal to the semiconductor base layer.

"In some embodiments, the non-uniform doping profile is a staircase doping profile.

"In some embodiments, the non-uniform doping profile is a hyper-abrupt doping profile.

"In some embodiments, the plurality of semiconductor layers positioned between the substrate and the semiconductor base layer includes a transition layer between the tuning layer and the semiconductor base layer.

"In some embodiments, the transition layer is a layer of the same material as the semiconductor base layer, but with a different doping type than a doping type of the semiconductor base layer.

"In some embodiments, a semiconductor device comprises a substrate, a transistor structure positioned on the substrate, and a varactor structure positioned on the substrate physically separated from the transistor structure. The varactor and the transistor have distinct instances of a common set of layers."

For the URL and additional information on this patent, see: Yang, Yuefei; Wang, Shing-Kuo. Monolithic HBT with Wide-Tuning Range Varactor. U.S. Patent Number 8716757, filed October 31, 2012, and published online on May 6, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=75&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3715&f=G&l=50&co1=AND&d=PTXT&s1=20140506.PD.&OS=ISD/20140506&RS=ISD/20140506

Keywords for this news article include: Electronics, Global Communication Semiconductors Inc..

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly