Metal–Semiconductor–Metal AlN Mid-Ultraviolet Photodetectors Grown by Magnetron Reactive Sputtering Deposition

Abstract

Metal–semiconductor–metal (MSM) AlN mid-ultraviolet (mid-UV) photodetectors were fabricated. AlN layers were grown on GaN substrates by magnetron reactive sputtering deposition. The AlN photodetectors exhibited a high responsivity at wavelengths from 210 nm to 190 nm, and the response tails off at a wavelength of 220 nm. The responsivities at 200 nm at biases of 5 V and 10 V were 1.08 and 3.51 A/W, respectively. When the reverse voltage was higher than 7 V, responsivity increased almost linearly with reverse voltage. The responsivity at 25 V was calculated to be approximately 14.9 A/W.

Fabrication study of AlN solar‐blind (<280 nm) MSM photodetectors grown by low‐temperature deposition

“…The effective Schottky barrier height (0.94 eV) deduced from the reverse I – V characteristics of the MSM devices deviates from the expected value of the difference between metal work function and the electron affinity of AlN. The result is similar to the reported literature 5, 19 and needs further investigation due to the possible existence of the interfacial layer and the uncertainty of the electron affinity of AlN 20–22.…”

“…It is also noted that the dark current of AlN MSM devices decreases with the increase in AlN film thickness. The dark current of AlN (1 µm)/GaN/sapphire MSM‐PD is 200 fA at 20 V bias, which, to the best of our knowledge, is the lowest reported in the literature using sputtering 5 and comparable to that prepared by MOCVD 6, 7. The low dark currents in the AlN MSM devices reflect the high crystalline quality and good Schottky contacts.…”

“…Several groups have proposed various types of GaN‐based UV sensors, such as p–n junction diodes, p–i–n diodes, Schottky barrier diodes, and metal–semiconductor–metal PDs (MSM‐PDs) 1–4. However, the III‐nitride based UV detector is still at an early stage of its development and only few reports are available concerning AlN for deep UV detection 5–7. AlN, possessing the largest direct bandgap and superior intrinsic properties, appears to be an ideal material for the development of novel solar‐blind (<280 nm) UV detectors.…”

“…AlN, possessing the largest direct bandgap and superior intrinsic properties, appears to be an ideal material for the development of novel solar‐blind (<280 nm) UV detectors. The growth of AlN film has been carried out by various methods, including metal organic chemical vapor deposition (MOCVD) 7, 8, molecular beam epitaxy (MBE) 9, 10, metal organic vapor phase epitaxy (MOVPE) 11, 12, and reactive magnetron sputtering 5, 13. In the first three methods, the process temperature is usually high and thus incompatible with other processes for the production of semiconductor integrated circuit devices.…”

A generalized Norde plot for reverse biased Schottky contacts

“…However, the interfacial properties of Schottky contacts are highly sensitive to both the fabrication method and the fabrication conditions, and thus the parameters extracted from the stand alone contacts differ from those of the actual contacts to a certain extent. Accordingly, some researchers [3] attempted to extract the contact parameters of the photodetector directly by measuring the dark current of the device. Assuming that the I-V characteristics of the contact conform to the basic thermionic emission theory [4][5], the barrier height φ and ideality factor n of the contact can be determined directly from the lnI vs. V plot.…”