Modeling of High Voltage AlGaN/GaN HEMT. Copyright 2008 Crosslight Software Inc.

Transcription

1 Modelin of Hih Voltae AlGaN/GaN HEMT Copyriht 2008 Crossliht Software Inc. 1

2 Introduction 2 AlGaN/GaN HEMTs - potential to be operated at hih power and hih breakdown voltae not possible for silicon or GaAs based technoloies. Numerous efforts explored to enhance the breakdown voltae of GaN based HEMT devices. The field plate (FP) structure effective for the hih breakdown voltae AlGaN/GaN HEMT desin but the field distribution in the drift reion needs optimization to minimize the specific on-resistance. In this work, modelin and optimization performed with the demonstration of remarkably hih breakdown voltae (900 V) for AlGaN/GaN HEMT with a manesium dopin layer under the 2-DEG channel by usin Crossliht APSYS.

3 Device structure Cross-section view of AlGaN/GaN HEMT structure with a M dopin layer. Chare density of cm -2 caused by the piezo-electric & polarization dipole modeled alon the upper side of the AlGaN/GaN interface to determine the 2DEG sheet carrier concentration. 3 Traps with its maximum concentration cm -3, relative enery level of 1.1eV also defined to ensure an semi-insulatin substrate. The substrate semi-insulatin traps effective in suppressin substrate parasitic conduction. Ref: G. Xie et al, in Proceedins of The 22nd International Symposium on Power Semiconductor Devices & ICs, Hiroshima, Japan, June 6-10, 2010

4 Material parameters used 4

5 Surface potential distribution 5 Reverse characteristics, alon the AlGaN/GaN interface (line B) for different M dopin layer lenth L, V GS =-5 V, drain voltae increased till breakdown; breakdown voltae as hih as 900V achieved with L=1.5 mm while only 560V for the conventional device without the manesium layer.

6 Impact ionization & breakdown I-V 6 Cutline alon y=7.0 mm; zero from x-axis left Cutline alon x=5.5 mm; zero from bottom I-V curve showin breakdown ~ 720 V; M dopin layer L~ 3.2 mm

7 Electric field distribution 7 Reverse characteristics, alon the AlGaN/GaN interface (line B) for different M dopin layer lenth L, V GS =-5 V. With a M layer, the electric field is spread between the drain and the ate. Without the M layer, the field peaks near the ede of the ate electrode.

8 Electric field 2D contours 8 The proposed AlGaN/GaN HEMT device with V GS = 5, V DS -breakdown= 900 V, L=1.5 mm Conventional HEMT structure of the same device dimension but without the M dopin layer showin breakdown only around 560 V

9 Breakdown vs M dopin layer 9 Breakdown voltaes as a function of the M layer s dopin concentration and width(lenth) at V GS = 5V. Breakdown voltae reaches its hihest value with a M dopin concentration of cm -3 for L=1.5, 2.5 and 3.5 mm.

10 2D current vectors reverse 10 Reverse characteristics, 2D current vectors the proposed HEMT after breakdown, showin majority of current flow throuh the substrate,v DS - breakdown= 900 V, V GS = 5 V

11 2D current vectors forward 11 Forward characteristics with applied V DS = 5 V, V GS = 0 V, the electron current flows throuh the quantum well.

12 Forward IV characteristics 12 The transistor exhibits ood pinch-off characteristics and a maximum drain current density of around 230A/m (per unit channel width) at a ate voltae of 0V.

13 Comparison of breakdown voltae versus specific on-resistance 13 Another important technique, device area manaement, can be used to improve the specific on-resistance and the breakdown voltae trade off. Ron-sp can be reduced by shrinkin excess areas such as contacts, ate-source offset and channel reions, dependin on the process.

14 Conslusion 14 Hih breakdown voltae AlGaN/GaN HEMT with the manesium layer structure simulated. Breakdown voltae of 900V is obtained by optimizin the manesium layer s lenth and its dopin concentration. The specific on resistance was 4 mw cm 2 with a breakdown voltae of 900 V usin a manesium layer lenth of 1.5 mm; its dopin concentration is cm -3 and the drift reion lenth is 10 μm. The manesium layer is deemed to be an effective mean to enhance the breakdown voltae of AlGaN/GaN devices.