Gallium arsenide heterojunction semiconductor structure

Patent metadata

Field	Value
Publication number	US-9761678-B2
Application number	US-201213655659-A
Country	US
Kind code	B2
Filing date	Oct 19, 2012
Priority date	Oct 20, 2011
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Embodiments of semiconductor structure are disclosed along with methods of forming the semiconductor structure. In one embodiment, the semiconductor structure includes a semiconductor substrate, a collector layer formed over the semiconductor substrate, a base layer formed over the semiconductor substrate, and an emitter layer formed over the semiconductor substrate. The semiconductor substrate is formed from Gallium Arsenide (GaAs), while the base layer is formed from a Gallium Indium Nitride Arsenide Antimonide (GaInNAsSb) compound. The base layer formed from the GaInNAsSb compound has a low bandgap, but a lattice that substantially matches a lattice constant of the underlying semiconductor substrate formed from GaAs. In this manner, semiconductor devices with lower base resistances, turn-on voltages, and/or offset voltages can be formed using the semiconductor structure.

First claim

What is claimed is:

1. A heterojunction bipolar transistor (HBT) comprising:
a semiconductor substrate formed from a Gallium Arsenide (GaAs) having a first lattice constant;
a base layer formed over the semiconductor substrate, wherein the base layer is epitaxial so as to be formed from a Gallium Indium Nitride Arsenide Antimonide (GaInNAsSb) crystal having a second lattice constant and having a first bandgap, wherein the second lattice constant substantially matches the first lattice constant of the GaAs crystal and wherein the GalnNAsSB crystal is doped such that the base layer is p-type;
a collector layer formed over the semiconductor substrate, wherein the collector layer is epitaxial so as to be formed from a third crystal having a third lattice constant that substantially matches the first lattice constant of the GaAs crystal, and wherein the third crystal is doped such that the collector layer is n-type and the base layer is formed on the collector layer so that a first heterojunction of the HBT is provided between the collector layer and so that the first heterojunction has first bandgap discontinuity;
an emitter layer formed over the semiconductor substrate wherein the emitter layer is epitaxial so as to be formed from an Indium Gallium Arsenide (InGaAs) crystal having a fourth lattice constant that substantially matches the first lattice constant of the GaAs crystal and wherein the InGaAs crystal is doped such that the emitter layer is n-type and the base layer is formed on the emitter layer so that a second heterojunction of the HBT is provided between the base layer and the emitter layer and so that the second heterojunction of the HBT has a second bandgap discontinuity, wherein the first bandgap discontinuity and the second bandgap discontinuity define a turn on voltage of the HBT and a knee voltage of the HBT;
an emitter cap layer formed over the emitter layer, the emitter cap layer being epitaxial so as to be formed from a fifth crystal, wherein the fifth crystal is doped so that the emitter cap layer is n-type, but such that doping is at a higher concentration than at the emitter layer; and
a subcollector layer formed beneath the collector layer, the subcollector layer being epitaxial so as to be formed from a sixth crystal, wherein the sixth crystal is doped so that the subcollector layer is n-type, but such that doping is at a higher concentration than at the collector layer.

2. The HBT of claim 1 wherein the GaInNAsSB crystal and the third crystal are configured to provide the first heterojunction such that the first bandgap discontinuity only includes a first valence bandgap discontinuity, and wherein the third crystal and the InGaAs crystal are configured such that the second bandgap discontinuity is divided between a second valence band discontinuity and a first conduction band discontinuity.

3. The HBT of claim 2 wherein the third crystal is selected from a group consisting of Aluminum Gallium Arsenide (AlGaAs) crystal and an Indium Gallium Phosphide (InGaP) crystal.

4. The HBT of claim 2 wherein the GaAs crystal is not doped.

Assignees

• Rf Micro Devices Inc
• Qorvo Us Inc

Inventors

• Moser Brian G
• Fresina Michael T

Classifications

• A61P37/02

  Immunomodulators · CPC title

• A61P11/06

  Antiasthmatics · CPC title

• H01L29/42304

  Electricity · mapped topic

• H01L29/205

  Electricity · mapped topic

• H01L29/7371

  Electricity · mapped topic