Photocathode having AlGaN layer with specified Mg content...

Details Photocathode having AlGaN layer with specified Mg content... Photocathode having AlGaN layer with specified Mg content...

2003-05-14

2004-12-14

Tran, Minhloan (Department: 2826)

Active solid-state devices (e.g., transistors, solid-state diode

Responsive to non-electrical signal

Electromagnetic or particle radiation

C257S010000, C257S011000, C313S542000

Reexamination Certificate

active

06831341

ABSTRACT:

TECHNICAL FIELD
This invention relates to a semiconductor photocathode, formed using a semiconductor as a component material, and which is excited by incident light and emits photoelectrons.
BACKGROUND ART
Conventional semiconductor photocathodes for use with ultraviolet light were formed for example from Al
x
Ga
1-x
N. Preexisting technology related to such semiconductor photocathodes formed from Al
x
Ga
1-x
N is disclosed in the specification of U.S. Pat. No. 5,557,167, the specification of U.S. Pat. No. 4,616,248, and in Japanese Patent Laid-open No. 08-96705. Conventional semiconductor photocathodes formed from Al
x
Ga
1-x
N have a quantum efficiency sufficient to enable practical application in the ultraviolet light.
DISCLOSURE OF THE INVENTION
However, when an attempt is made to perform precise measurements, the quantum efficiency of such conventional semiconductor cathodes cannot be described as sufficient, and Al
x
Ga
1-x
N system semiconductor photocathodes with still higher quantum efficiencies are desired. The present invention is intended to resolve this problem, and has as an object the provision of a semiconductor photocathode with high quantum efficiency, having an optical absorption layer formed from Al
x
Ga
1-x
N (0≦x≦1).
Upon conducting advanced studies and research to improve the quantum efficiency of this type of semiconductor photocathode, the inventors discovered that the quantum efficiency depends heavily on the content concentration of Mg in the Al
x
Ga
1-x
N layer (0≦x≦1) which is the optical absorption layer.
This invention is a semiconductor photocathode which is excited by incident light and emits photoelectrons, and is characterized in that an optical absorption layer which absorbs incident light and causes the generation of photoelectrons is formed from an Al
x
Ga
1-x
N layer (0≦x≦1) with an Mg content concentration of 2×10
19
cm
−3
or higher and 1×10
20
cm
−3
or less. In this case, the quantum efficiency can be improved over that of the prior art.
Further, this invention is characterized in that the Al
x
Ga
1-x
N layer forming the optical absorption layer has a composition ratio x of 0.3≦x≦0.4. Through such a configuration, a so-called solar-blind type semiconductor photocathode can be realized.


REFERENCES:
patent: 3986065 (1976-10-01), Pankove
patent: 4616248 (1986-10-01), Khan et al.
patent: 5557167 (1996-09-01), Kim et al.
patent: 08096705 (1996-04-01), None
patent: 08153462 (1996-06-01), None
patent: 2000030604 (2000-01-01), None
patent: WO 9703453 (1997-01-01), None
C. Stampfl, et al.,Doping of AlxGa1-xN,Appl. Phys. Lett. 72(4), Jan. 26, 1998, pp. 459-461.
M.A. Khan et al.,Properties and ion implantation of AlzGa1-xN epitaxial single crystal films prepared by low pressure metalorganic chemical vapor deposition,App. Phys. Lett. 43 (5), Sep. 1, 1983, pp. 492-494.
C. Stampfl et al., Doping of AlGaN, Appl. Phys. Lett. 72(4) Jan. 26, 1998; pp. 459-461.
M.A. Khan et al., Properties and ion implantation of AlGaN epitaxial single crystals prepared by low pressure metalorganic chemical vapor deposition, Appl. Phys. Lett. 43 5 Sep. 1, 1983, pp. 492-494.

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