AlGaN/GaN Heterostructure Field-Effect Transistors on Fe-Doped GaN Substrates with High Breakdown Voltage

Abstract

AlGaN/GaN heterostructure field-effect transistors (HFETs) were fabricated by metalorganic vapor phase epitaxy (MOPVE) on c-plane Fe-doped GaN (GaN:Fe) substrates with different growth conditions of GaN buffer layers. The GaN buffer layers were grown at a V/III ratio of 272 at 300 Torr to realize highly resistive GaN buffer layers with automatic carbon doping. HFETs with carbon-doped GaN buffer layers showed the best characteristics among all the samples in this study. The carbon concentration was 5 Â 10 16 cm À3 . In the sample with a gate-drain length of 50 m, the off-state breakdown voltage was 2 kV or higher and the on-resistance was 18.5 mÁcm 2 . We found that the carbon-doped GaN buffer layers are necessary for high breakdown voltages even using semi-insulating GaN:Fe substrates. #

Mapping of contactless photoelectrochemical etched GaN Schottky contacts using scanning internal photoemission microscopy—difference in electrolytes

“…For this reason, capacitive-coupled and inductive-coupled plasma (ICP) reactive-ion-etching methods have been widely used for device isolation etching and the gate recess etching of AlGaN/GaN HEMTs. [3][4][5][6][7][8][9] Although ICP is widely used for the etching of GaN, damage caused by plasma is a serious concern in terms of the device's stability and reliability. [10][11][12][13][14] On the other hand, PEC etching is basically a damageless etching system because it is a plasma-free process.…”

Mapping of photo-electrochemical etched Ni/GaN Schottky contacts using scanning internal photoemission microscopy—comparison between n- and p-type GaN samples

“…However, GaN is a robust material and no practical wet-chemical approach is so far available in device fabrication. Therefore, reactive-ion etching and inductively coupled plasma (ICP) methods have been widely used for mesa isolation etching for p-n diodes, 1,2) lateral Schottky barrier diodes (SBDs), HEMTs, 3,4) bipolar transistors, 5,6) and laser diodes, 7,8) and the gate recess etching of AlGaN/GaN HEMTs, [9][10][11][12][13][14][15][16] Although ICP is widely used for the etching of GaN, plasma-induced damage is a serious concern in terms of device stability and reliability. [17][18][19][20][21] On the other hand, the PEC etching is a basically damage-less etching system because it is a plasma-free process.…”

MOCVD of Nitrides

“…Owing to the surface segregation of Fe, however, the channel mobility is degraded by unintentional Fe doping into the channel layer [85][86][87]. To fabricate high-power HFETs, the growth of a highly resistive GaN layer is necessary.…”