Microchannel plate photocathode

• US 20100025796A1
• Filed: 08/03/2009
• Published: 02/04/2010
• Est. Priority Date: 08/04/2008
• Status: Abandoned Application

• Current Assignee: Amir Massoud Dabiran
• Original Assignee: Amir Massoud Dabiran
• Inventors: Dabiran, Amir Massoud
• Application Number:
  US12/462,387
• Publication Number:
  US 20100025796A1
• Time in Patent Office: Days
• US Class Current: 257/436
• CPC Class Codes: C23C 16/403 of aluminium, magnesium or beryllium
• CPC Class Codes: C23C 16/45525 Atomic layer deposition [ALD]
• CPC Class Codes: H01J 31/507 using a large number of channels, e.g. microchannel plates
• CPC Class Codes: H01J 9/125 of secondary emission electrodes
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• CPC Class Codes: H01L 31/022408 for devices characterised by at least one potential jump barrier or surface barrier

Abstract

An energy-enhanced, low-temperature growth technique is used for direct deposition of periodic table column III nitrides-based negative electron affinity (NEA) photocathodes on standard glass microchannel plates (MCPs.) As working examples, low-temperature RF plasma-assisted molecular beam epitaxy growth (MBE) of p-type GaN layers on sapphire, quartz, and glass and alumina MCPs and their photoemission characterization is disclosed.

Claims

1. A method for providing a photocathode layer structure on a substrate of a substrate material differing from that the layers in the photocathode layer structure, the method comprising:

heating the substrate to a temperature less than the thermal damage temperature of the substrate material, and

depositing on the substrate a semiconductor material selected from magnesium doped GaN, AlGaN and InGaN, to thereby form thereon a growth layer with a growth surface, while increasing the energy of reactants at the growth surface from a source of energy external to the substrate without increasing the growth temperature of the substrate past the thermal damage temperature of the substrate material.

2. The method of claim 1 further comprising cleaning the substrate surface prior to depositing on the substrate a semiconductor material.

3. The method of claim 2 further comprising preceding the depositing on the substrate of a semiconductor material with depositing on the substrate a protective layer preventing diffusion therethrough from the substrate.

4. The method of claim 2 further comprising preceding the depositing on the substrate of a semiconductor material with depositing on the substrate a nucleating layer to promote starting the deposition of the semiconducting material growth layer to be supported on the substrate.

5. The method of claim 1 further comprising preceding the depositing on the substrate of a semiconductor material with depositing on the substrate a protective layer preventing diffusion therethrough from the substrate.

6. The method of claim 1 further comprising preceding the depositing on the substrate of a semiconductor material with depositing on the substrate a nucleating layer to promote starting the deposition of the semiconducting material growth layer to be supported on the substrate.

7. The method of claim 1 wherein the depositing on the substrate a semiconductor material is accomplished by radio frequency plasma assisted molecular beam epitaxy.

8. The method of claim 7 wherein the substrate is a microchannel plate.

9. The method of claim 1 wherein the substrate is a microchannel plate.

10. A method for providing a photocathode structure on a substrate, the method comprising:

a) chemical and vacuum thermal cleaning of the substrate;

b) heating the substrate in a vacuum chamber to ˜

300°

C.;

c) deposition of a thin (˜

10 to ˜

50 nm) of Al₂O₃ layer by ALD at ˜

250°

C.; and

d) deposition of p-type (Mg-doped) GaN (or AlGaN or InGaN) on the Al₂O₃ covered substrate by RF plasma-enhanced MBE at ˜

230°

C.

11. The method of claim 10 wherein the deposition of p-type (Mg-doped) GaN (or AlGaN or InGaN) on the Al₂O₃ covered substrate by RF plasma-enhanced MBE is at ˜

300°

C.

12. The method of claim 10 wherein the deposition of p-type (Mg-doped) GaN (or AlGaN or InGaN) on the Al₂O₃ covered substrate by RF plasma-enhanced MBE is at ˜

350°

C.

13. The method of claim 10 wherein the substrate is a microchannel plate.

14. A photodetector having a microchannel plate having a periodic table column III nitride material photocathode on surfaces thereof, the photodetector comprising:

a microchannel plate having an end surface interrupted by a plurality of microchannels opening therein,

a semiconductor material photocathode layer supported by the end surface and by sides of each of the plurality of microchannels with the semiconductor material being selected from magnesium doped GaN, AlGaN and InGaN, and

a negative electron affinity material layer provided on the semiconductor material photocathode layer having a lower electron affinity than does the semiconductor material photocathode layer.

15. The photodetector of claim 14 further comprising a protective layer between the semiconductor material photocathode layer and the end surface and between the semiconductor material photocathode layer and the sides of the plurality of microchannels.