Ultra-low turn-on voltage and on-resistance vertical GaN-on-GaN Schottky power diodes with high mobility double drift layers

Abstract

This letter reports the implementation of double-drift-layer (DDL) design into GaN vertical Schottky barrier diodes (SBDs) grown on free-standing GaN substrates. This design balances the trade-off between desirable forward turn-on characteristics and high reverse breakdown capability, providing optimal overall device performances for power switching applications. With a wellcontrolled metalorganic chemical vapor deposition process, the doping concentration of the top drift layer was reduced, which served to suppress the peak electric field at the metal/GaN interface and increase the breakdown voltages of the SBDs. The bottom drift layer was moderately doped to achieve low on-resistance to reduce power losses. At forward bias, the devices exhibited a record low turn-on voltage of 0.59 V, an ultra-low on-resistance of 1.65 mX cm 2 , a near unity ideality factor of 1.04, a high on/off ratio of $10 10 , and a high electron mobility of 1045.2 cm 2 /(V s). Detailed comparisons with conventional single-drift-layer (SDL) GaN vertical SBDs indicated that DDL design did not degrade the forward characteristics of the SBDs. At reverse bias, breakdown voltages of the DDL GaN SBDs were considerably enhanced compared to those of the conventional SDL devices. These results showed that GaN vertical SBDs with DDL designs are promising candidates for high efficiency, high voltage, high frequency power switching applications.

Vertical GaN-on-Si MOSFETs With Monolithically Integrated Freewheeling Schottky Barrier Diodes

“…The integrated SBD in this work was benchmarked against state-of-the-art vertical SBDs on silicon, sapphire and GaN substrates in Fig. 5, revealing state-of-the-art performance compared to vertical GaN-on-Si SBDs [17], [18], [27][28][29][30][31][32][33][34][35][36][37][38]. The V BR of the integrated MOSFET-SBD can be significantly improved: 1.…”

“…The V BR of the integrated MOSFET-SBD can be significantly improved: 1. By using low-defect-density GaN substrates [27], [29], [30]; 2. By increasing the drift layer thickness and further reducing the background carrier concentration from 2×10 16 cm -3 in this work to ~10 15 cm -3 [30], [31]; 3.…”

“…By using low-defect-density GaN substrates [27], [29], [30]; 2. By increasing the drift layer thickness and further reducing the background carrier concentration from 2×10 16 cm -3 in this work to ~10 15 cm -3 [30], [31]; 3. By employing field plate, edge termination, and guard ring technologies [32][33][34]; 4.…”

Review of the Recent Progress on GaN-Based Vertical Power Schottky Barrier Diodes (SBDs)

“…After that, the samples were annealed at a certain condition to further improve the ohmic behavior. (Ti/Al/Ni/Au at 600-840 • C in N 2 for 20-30s [2,26,29,33,65,67,71,72]; Ti/Al/Pt/Au at 700 • C-850 • C in N 2 for 30s [5,53,54,86]; Ti/Al [19,31,37,38,68,75,76,82]; Ti/Al/Ti/Au [32,67,83,87]; Ti/Al/Au [18,81].) Then, the nickel layer is formed on ohmic contact metal by an electroplating process, as shown in Figure 11b.…”

GaN-Based Schottky Diode

“…It was reported that the structure greatly reduced the on-state resistance [36]. Fu et al made further improvement to MOCVD regrown drift layers on HVPE substrate by introducing double-drift-layer (DDL) design [37]. An additional moderately doped GaN layer was inserted in between the lightly doped top layer and the highly doped bottom layer.…”