The Leakage Current of the Schottky Contact on the Mesa Edge of AlGaN/GaN Heterostructure

Abstract

A test structure, which is called the ridge-furrow structure, is used to evaluate the leakage current of the Schottky contact on the mesa edge of an AlGaN/GaN heterostructure. The mesa edge leakage currents were measured at different temperatures from 300 to 500 K and analyzed. The conduction-band-edge energy distribution at the mesa edge is simulated by the Integrated Systems Engineering Technology Computer-Aided Design. Based on the simulation results, the electric field strength can be obtained as a function of reverse bias voltage. The mesa edge leakage current is found to agree with the predicted characteristics, which is based on the Frenkel-Poole emission model. Therefore, we believe that the Frenkel-Poole emission dominates the mesa edge leakage at temperatures between 300 and 500 K.Index Terms-AlGaN/GaN, characteristic electric field strength, Frenkel-Poole, leakage current, mesa edge, ridge-furrow structure.

Leakage current by Frenkel–Poole emission in Ni/Au Schottky contacts on Al0.83In0.17N/AlN/GaN heterostructures

“…11 Zhang et al 7 analyzed the leakage current mechanisms in the Schottky contacts of both n-GaN and AlGaN/GaN at different temperatures and concluded that tunneling current dominates at temperatures below 150 K, whereas the Frenkel-Poole emission dominates at temperatures higher than 250 K. Miller et al 8 have shown that the reverse-bias leakage in AlGaN/GaN can be analyzed in a conventional tunneling model. The effects of the dislocations and defects states, in the reverse-bias leakage, have been suggested by several studies for GaN and Al x Ga 1−x N heterostructures 4,6,7 wherein defects, in particular dislocations, might play an important role in reverse-bias leakage. 4,7,8 However, to date, no investigation has been made to analyze the leakage current of the mechanisms of Schottky contacts on Al 1−x In x N / AlN/ GaN heterostructures.…”

“…[4][5][6]12 In the case of dominant dislocation-related conductivity in the leakage current at room temperature for Al 0.83 In 0.17 N / AlN/ GaN Schottky diodes, we required in our analysis that a single transport mechanism must accurately describe the current flow. The transport model based on Frenkel-Poole emission satisfied this criterion and gives realistic values for the necessary physical parameters.…”

“…It can be concluded that emission into or from dislocation-related trapped states, or conduction along dislocation lines, should be the dominant factor determining the electric field and temperature dependence of the leakage current density. 6,7,15 The threading dislocation density for the GaN based high electron mobility transistor structures grown on sapphire substrate are given on the order of 10 8 cm −2 . 12 The dislocation density for Al 0.83 In 0.17 N / AlN/ GaN heterostructure were measured as 5.9ϫ 10 8 cm −2 in this study.…”

The Effect of Forward Gate Bias Stress on the Noise Performance of Mesa Isolated GaN HEMTs

“…Measurements were performed on 0.25 μm gate length AlGaN/GaN HEMTs fabricated in a Chalmers in-house MMIC process [9]. For the noise measurements, devices with 4 × 75 μm gate periphery were used.…”

“…We specifically address the case where the devices are isolated using an etched mesa, with the gate fingers extending outside the mesa and directly contacting the GaN channel through the mesa sidewall, giving rise to an additional conduction path for the gate current. The effect of this leakage path on the reverse leakage has been studied in [9], but the effects on device robustness have previously not been tested. Moreover, it is shown how degradation tests on device level can be used to analyze or optimize robustness of LNAs using circuit level simulations.…”