Showing papers by "Tsutomu Uesugi published in 2019"
TL;DR: In this article, homoepitaxial GaN p-n junction diodes with a negative beveled-mesa termination were investigated using TCAD simulation, and the devices were designed using currently available GaN growth techniques.
Abstract: We report on homoepitaxial GaN p-n junction diodes with a negative beveled-mesa termination. The electric field distribution in a beveled-mesa was investigated using TCAD simulation, and the devices were designed using currently available GaN growth techniques. Shallow-angle (ca. 10°) negative bevel GaN p-n junction diodes were fabricated with various Mg acceptor concentrations in the p-layers. The suppression of electric field crowding and improvement of the breakdown voltage were observed, as the Mg concentration was decreased. The parallel-plane breakdown field of 2.86 MV/cm was obtained for a device with the breakdown voltage of 425 V.
64 citations
TL;DR: Avalanche multiplication characteristics of GaN p-n junction diodes with double-side-depleted shallow bevel termination, which exhibit nearly ideal avalanche breakdown, were investigated by photomultiplication measurements using subbandgap light as mentioned in this paper.
Abstract: Avalanche multiplication characteristics of GaN p-n junction diodes (PNDs) with double-side-depleted shallow bevel termination, which exhibit nearly ideal avalanche breakdown, were investigated by photomultiplication measurements using sub-bandgap light. In GaN PNDs under reverse bias conditions, optical absorption induced by the Franz-Keldysh (FK) effect is observed, resulting in a predictable photocurrent. The avalanche multiplication factors were extracted as a ratio of the measured values to the calculated FK-induced photocurrent. In addition, the temperature dependences of the avalanche multiplications were also investigated.
26 citations
TL;DR: In this article, the authors analyzed forward currentvoltage (I-V) characteristics in GaN-on-GaN p-n+ junction diodes with mesa-isolation structure and obtained an SRH lifetime of 46 ps at 298 K.
Abstract: The Shockley–Read-Hall (SRH) lifetime in homoepitaxial p-GaN (N a = 1 × 1017 cm−3) is investigated by analyzing forward current–voltage (I–V) characteristics in GaN-on-GaN p–n+ junction diodes with mesa-isolation structure. The ideality factor around 2 due to recombination current was obtained in the 1.8–2.7 V window, which is different from the characteristic of a p+-n− junction involving considerable diffusion current. The recombination current was proportional to the junction area, indicating that the recombination current is a bulk component, not a mesa-surface component. Analyzing the recombination current with consideration of the SRH recombination rate in the depletion layer, we obtained an SRH lifetime of 46 ps at 298 K. The temperature dependence of the I–V characteristics was also investigated and the SRH lifetimes were extracted in the range of 223–573 K. The SRH lifetime in homoepitaxial p-GaN followed the empirical power law of = 1.2 × 10−16 × T 2.25 (s).
17 citations
19 May 2019
TL;DR: In this article, the authors investigated the valanche multiplication characteristics in GaN p-n junction diodes under high reverse bias conditions and showed that the photocurrent induced by the Franz-Keldysh effect can be well reproduced by the theoretical calculations of the optical absorption, and their avalanche multiplications were observed.
Abstract: A valanche multiplication characteristics in GaN p-n junction diodes (PNDs) under high reverse bias conditions were investigated. The GaN-on-GaN PNDs with double-side-depleted shallow bevel termination, which showed low reverse leakage current and excellent avalanche capability, were used for the measurements. Under sub-bandgap light illumination, the photocurrents induced by Franz-Keldysh (FK) effect, which can be well reproduced by the theoretical calculations of the optical absorption, and their avalanche multiplications were observed. The multiplication factors were extracted as the ratios of the experimental photocurrents to the calculated FK-induced photocurrent. Under an assumption of equal impact ionization coefficients of electrons and holes, the electric-field dependence of an impact ionization coefficient in GaN were estimated.
3 citations