Zn(MgBe)Se ultraviolet photodetectors

We present the growth and characterization of blue-violet and ultraviolet photodetectors based on ZnSe and Zn(Mg)BeSe compounds. Structures are grown by molecular beam epitaxy on (001) GaAs substrates. Three types of photodetectors have been fabricated. Zn(Mg)BeSe p-i-n photodiodes exhibit a high response of 0.17 A/W with a rejection rate of 104 and a wavelength cutoff of 450 nm. Schottky barrier photodiodes based on planar geometry devices display a very flat response above the band gap with a rejection rate above 103. High responses with quantum efficiency higher than 50% have been obtained. The wavelength cutoff can be tuned from 460 (ZnSe) to 380 nm (ZnMgBeSe), which leads to visible blind devices. Detectivities from 2.0 1010 (ZnMgBeSe) to 1.3 1010 mHz1/2W−1 (ZnSe) have also been measured. Metal-semiconductor-metal devices, recently fabricated, exhibit a spectral response very similar to Schottky devices. Quantum efficiencies of 40% are easily obtained in these devices with a rejection rate of 103.