Characteristics of GaN material and application in UV detection

Abstract

For the characteristics such as wide bandgap, low dielectric constant, ability to bear high temperature, ability to resist radiation etc., GaN material can be used for UV solar blind detection in very rigorous environments. But for a long time, the preparation technology for GaN material has been still keeping it from being used extensively. GaN photocathode with good future is developed slowly in the field of UV detection. The key method of obtaining effective photoemission is to reduce the vacuum energy level of GaN emission surface, make it lower than bulk conduction band minimum. Negative electron affinity (NEA) GaN photocathode can convert the light under 365 nm to the photoelectrons that can be sent to the free space. The surface potential of NEA GaN photocathode is made up of two straight line sections with different slope. As the first dipole layer, [GaN(Mg):Cs] dipole brings 3.0 eV decline of the vacuum energy level, make the GaN photocathode surface obtain about -1.0 eV effective negative electron affinity. The second dipole O-Cs makes effective electron affinity reduce further to - 1.2 eV. The results show: near 37% quantum efficiency can be gotten at the wavelength 200 nm for reflection-mode GaN photocathode, and the quantum efficiency reaches up to 13% at 290 nm in transmission mode. The large quantum efficiency and high stability are very good properties for UV detection devices employing GaN photoemitter.