Breakdown characteristics of deep-ultraviolet Al0.6Ga0.4N p-i-n avalanche photodiodes

Abstract

A top-illuminated deep-ultraviolet Al0.6Ga0.4N p-i-n avalanche photodiode (APD) structure was designed and grown by metalorganic chemical vapor deposition on an AlN bulk substrate and on two different quality AlN/sapphire templates, and APDs were fabricated and tested. The APD devices with a circular diameter of 20 μm have demonstrated a distinctive reverse-bias breakdown behavior. The reverse breakdown voltage of the APDs is approximately −140 V, which corresponds to a breakdown electric field of 6–6.2 MV/cm for the Al0.6Ga0.4N material as estimated by Silvaco TCAD simulation. The APDs grown on the AlN bulk substrate show the lowest leakage current density of <1 × 10−8 A/cm2 (at low reverse bias) compared to that of the devices grown on the AlN templates. From the photocurrent measurement, a maximum gain (current limited) of 1.2 × 104 is calculated. The average temperature coefficients of the breakdown voltage are negative for APD devices fabricated from both the AlN bulk substrate and the AlN templates, but these data show that the coefficient is the least negative for the APD devices grown on the low-dislocation-density AlN bulk substrate.

Progress on photovoltaic AlGaN photodiodes for solar-blind ultraviolet photodetection

“…The crystal quality of AlGaN grown on a bulk AlN substrate is intrinsically expected to be good because they both have the same crystallographic symmetry of wurtzite. Therefore, the use of the bulk AlN substrate during the photodetectors manufacturing is worth investigation [19][20][21][22][23][24][25] . For example, Jeong et al reported topilluminated Al 0.6 Ga 0.4 N p-i-n SBPDs grown on an AlN bulk substrate and on another two types of AlN templates with different quality [19] .…”

“…Therefore, the use of the bulk AlN substrate during the photodetectors manufacturing is worth investigation [19][20][21][22][23][24][25] . For example, Jeong et al reported topilluminated Al 0.6 Ga 0.4 N p-i-n SBPDs grown on an AlN bulk substrate and on another two types of AlN templates with different quality [19] . They found that the peak of the AlGaN SBPD grown on the AlN bulk substrate has a narrower linewidth compared to those of the AlGaN SBPDs grown on the AlN/sapphire templates in X-ray diffraction-based reciprocal space mapping.…”

The Insertion of an AlN Spacer between the Barrier and the Channel Layer for a Polarization-Enhanced AlGaN-Based Solar-Blind Ultraviolet Detector

“…SBUV light is usually very weak, making high gain and low dark current crucial for the detection. AlGaN SBUV detectors with internal gain, such as photoconductors and avalanche photodiodes (APDs), have been extensively studied. − However, the photoconductors typically exhibit slow speed and high dark current due to the defect trapping effect. , Besides, although the APDs can achieve high gain, low dark current, and fast speed, the requirement of high-quality materials, high-efficient p-doping, high operating bias, and complex driving circuit limits their application. ,− …”