Voltage tunable solar blindness in TFS grown EG/SiC Schottky contact bipolar phototransistors

Patent metadata

Field	Value
Publication number	US-11309449-B2
Application number	US-201816624402-A
Country	US
Kind code	B2
Filing date	Jun 27, 2018
Priority date	Jun 27, 2017
Publication date	Apr 19, 2022
Grant date	Apr 19, 2022

Abstract

A voltage tunable solar-blind UV detector using a EG/SiC heterojunction based Schottky emitter bipolar phototransistor with EG grown on p-SiC epi-layer using a chemically accelerated selective etching process of Si using TFS precursor.

First claim

What is claimed is:

1. A bipolar junction transistor comprising:
an upper epitaxial graphene emitter layer grown on a selectively etched intermediate p-SiC epilayer, wherein selective etching of the intermediate p-SiC epilayer occurs via a homoepitaxy compatible Tetra-Fluoro-Silane gas precursor;
an n + SiC substrate layer; and
the upper epitaxial graphene emitter laver, intermediate p-SiC epilayer and the n + SiC substrate layer are vertically stacked to form an:
epitaxial graphene/SiC heterojunction-based;
voltage tunable;
solar-blind;
UV detector with a peak wavelength responsivity shift from 320 nm to less than 250 nm dependent upon a bias voltage applied at the epitaxial graphene emitter layer.

2. The bipolar junction transistor of claim 1 , wherein dopant concentration of the epilayer is p-type and ranges between 3×10 14 cm −3 to 4×10 14 cm −3 .

3. The bipolar junction transistor of claim 1 with photoresponsivity of substantially 17- 25 A/W at a bias voltage =20 V.

4. The bipolar junction transistor of claim 1 , wherein the upper epitaxial graphene emitter layer is transparent.

5. The bipolar junction transistor of claim 1 further comprising detection and discrimination of ultraviolet radiation ranging from 200-400 nm at low bias voltage.

6. The bipolar junction transistor of claim 1 further comprising a UV-visible rejection ratio of >10 3 .

7. The bipolar junction transistor of claim 1 further wherein p-SiC epilayer thickness ranges from 0.1 μm -100 μm.

8. The bipolar junction transistor of claim 1 , wherein the thickness of the upper epitaxial graphene emitter layer ranges from 1 monolayer to 20 monolayers.

9. A method of forming a bipolar junction transistor comprising:
growing a p-SiC epilayer on an n + SiC substrate layer substrate via a CVD reactor; and
growing an epitaxial graphene top electrode layer on the p-SiC epilayer by selective etching of Si from SiC using a Tetra-Fluoro-Silane gas precursor;
vertically stacking the epitaxial graphene top electrode layer, intermediate p-SiC epilayer and the n + SiC substrate layer to form an:
epitaxial graphene/SiC heterojunction-based;
voltage tunable;
solar-blind UV detector; and

applying a bias voltage to the epitaxial graphene top electrode layer to shift a peak wavelength responsivity from 320 nm to less than 250 nm dependent upon the bias voltage applied.

10. The method of 9 , wherein the CVD reactor uses dichlorosilane and propane in hydrogen ambient at 300 Torr and 1600 C.

11. The method of claim 10 , wherein the C/Si ratio may range from 1.5 to 1.9.

12. The method of claim 9 , wherein dopant concentration of the p-SiC epilayer is p-type and ranges between 3×10 – cm −3 to 4×10 14 cm −3 .

13. The method of claim 9 , wherein the EG top electrode layer is grown on the p-SiC epilayer at 1600° C. and 300 Torr.

14. The method of claim 13 , wherein a SiF 4 precursor in Argon is used to grow the EG top electrode layer on the p-SiC epilayer.

15. The method of 9 , wherein substantially circular graphene regions are defined using photolithography followed by O 2 plasma reactive-ion etching.

16. The method of 15 , wherein the substantially circular graphene mesa regions have a diameter of substantially 250 μm.

17. The method of 9 , wherein the thickness of the EG top electrode layer is ranges from 1 monolayer to 20 monolayers.

Assignees

• Univ South Carolina

Inventors

• Chava Venkata Surya N
• Chandrashekhar Mvs
• Balachandran Anusha

Classifications

• H10P14/24

  using chemical vapour deposition [CVD] · CPC title

• H10P14/38

  characterised by treatments done after the formation of the materials · CPC title

• H10P14/20

  of semiconductor materials · CPC title

• H10P14/3406

  Carbon, e.g. diamond-like carbon · CPC title

• H10P14/2926

  Crystal orientations · CPC title