Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers
A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.
1. A semiconductor device comprising:
a Si substrate;
a compliant buffer layer comprising crystalline Al, wherein the compliant buffer layer is coincident site lattice-matched to the Si substrate, and the compliant buffer layer has a face-centered cubic structure; and
a device layer comprising a first crystalline semiconductor material chosen from III-V semiconductor materials, III-V semiconductor alloys, II-VI semiconductor materials, II-VI semiconductor alloys, Ge, SiGe, and group IV semiconductor alloys, wherein the device layer is coincident site lattice-matched to the compliant buffer layer.
2. The device of claim 1 , wherein the device layer further comprises at least one additional crystalline semiconductor material chosen from III-V semiconductor materials, III-V semiconductor alloys, II-VI semiconductor materials, II-VI semiconductor alloys, Ge, SiGe, and group IV semiconductor alloys, wherein the at least one additional crystalline semiconductor material is lattice-matched to the first crystalline semiconductor material.
3. The device of claim 1 or claim 2 , wherein the semiconductor device is chosen from a photovoltaic solar cell, a LED, a laser, a transistor, a high electron mobility transistor, and a light detector.
4. The device of claim 3 , wherein the semiconductor device is a two-junction PV solar cell, the first crystalline semiconductor material comprises GaAs having a band gap of about 1.4 eV, and the at least one additional semiconductor material comprises GaInP having a band gap of about 1.9 eV.
5. The device of claim 3 , wherein the semiconductor device is a three junction PV solar cell, the first crystalline semiconductor material comprises GaAs having a band gap of about 1.4 eV, the at least one additional semiconductor material comprises GaInP having a band gap of about 1.9 eV, and the Si substrate functions as a semiconductor material having a band gap of about 1.1 eV.
6. The device of claim 3 , wherein the semiconductor device is an LED and the first crystalline semiconductor material comprises InGaN having a band gap ranging between about 1.9 eV and about 2.5 eV.
7. The device of claim 3 , wherein the semiconductor device is a high electron mobility transistor, the first crystalline semiconductor material comprises an AlGaSb semiconductor material, and the at least one additional semiconductor material comprises:
a first AlSb barrier layer lattice-matched on the AlGaSb semiconductor material;
an InAs quantum well channel layer lattice-matched on the first AlSb layer;
a second AlSb spacer layer lattice-matched on the InAs QW channel layer;
a delta-doped InAs quantum well layer lattice-matched on the second AlSb spacer layer;
a third AlSb barrier layer lattice-matched on the delta doped InAs quantum well layer; and,
an InAs top contact layer lattice-matched on the second AlSb barrier layer.
8. The device of claim 1 , wherein the compliant buffer layer consists essentially of crystalline Al.
9. The device of claim 1 , wherein a ratio of a lattice constant of the compliant buffer layer to a lattice constant of the device layer is less than or equal to ¾.
10. The device of claim 1 , wherein a ratio of a lattice constant of the compliant buffer layer to a lattice constant of the device layer is greater than or equal to 6(√2)/7.