Trapping effects and microwave power performance in AlGaN/GaN HEMTs

Abstract

The dc, small-signal, and microwave power output characteristics of AlGaN/GaN HEMTs are presented. A maximum drain current greater than 1 A/mm and a gate-drain breakdown voltage over 80V have been attained. For a 0.4 m gate length, an of 30 GHz and an max of 70 GHz have been demonstrated. Trapping effects, attributed to surface and buffer layers, and their relationship to microwave power performance are discussed. It is demonstrated that gate lag is related to surface trapping and drain current collapse is associated with the properties of the GaN buffer layer. Through a reduction of these trapping effects, a CW power density of 3.3 W/mm and a pulsed power density of 6.7 W/mm have been achieved at 3.8 GHz.

Deep traps in AlGaN/GaN heterostructures studied by deep level transient spectroscopy: Effect of carbon concentration in GaN buffer layers

“…As U p increases to Ϫ3 V, corresponding to detection near the 2DEG channel, we observe ͑i͒ the appearance of a negatively going holelike trap H 1 at 510 K in the low-͓C͔ SBD and a holelike trap H 2 at T Ͼ 550 K in the high-͓C͔ SBD; and ii͒ an increase in traps A x and A 1 in the low-͓C͔ sample and A 1 and A 2 in the high-͓C͔ sample, which is due to an increase in the detection volume. As U P further increases from Ϫ3 to 1 V, corresponding to detection across the 2DEG channel, we observe i͒ a significant increase in H 1 in the low-͓C͔ SBD and H 2 in high-͓C͔ SBD ͑H 2 had not peaked before the upper temperature limit was reached͒; ͑ii͒ almost no change in the electron traps ͑A x and A 1 ͒ in the low-͓C͔ SBD and ͑A 1 and A 2 ͒ in the high-͓C͔ SBD; and ͑iii͒ a significant decrease in the electron traps, A 2 in the low-͓C͔ SBD and A 3 in the high-͓C͔ SBD, which is due to the influence of increased negatively going H 1 6 In Ref. 6, two holelike traps ͑0.29 and 0.55 eV͒ were attributed to surface states of the HFET, since they became small in devices passivated with Si 3 N 4 .…”

“…From these Arrhenius plots, shown in the insets of Figs. 4͑a͒ and 4͑b͒, values of the activation energy and capture cross section were determined to be 1.24 eV and 5 ϫ 10 −12 cm 2 for the holelike trap H 1 and 0.99 eV and 1.5ϫ 10 11 cm 2 for the electron trap A 1 . These values are similar to those observed for trap A 1 , previously reported by our laboratory for AlGaN/GaN SBDs from other source.…”

“…Early studies revealed that gate lag and drain current collapse in HFET devices were related to traps in the AlGaN surface and GaN buffer layers. 1 Many techniques, such as photoionization spectroscopy, 2 deep level transient spectroscopy ͑DLTS͒, 3 deep level optical spectroscopy ͑DLOS͒, 4,5 and current-DLTS on HFETs, 6 have been used to study traps in AlGaN/GaN structures. Carbon is a common residual impurity in unintentionally doped ͑UID͒ GaN buffer layers grown by metalorganic chemical vapor deposition ͑MOCVD͒ but the carbon concentration and resistivity in these layers can be controlled by growth pressure.…”

Non-localized trapping effects in AlGaN/GaN heterojunction field-effect transistors subjected to on-state bias stress

“…Here, V GS and V DS are the gate and drain biases, respectively, and V T is the threshold voltage. Almost simultaneously, Binari et al 3 and Vetury et al 4 proposed different models to explain current collapse. Binari et al attributed on-stress-and off-stress-induced current collapse to GaN buffer traps and AlGaN surface traps, respectively.…”

Current transport mechanism in graphene/AlGaN/GaN heterostructures with various Al mole fractions

“…[7][8][9] All of these distinct characteristics are useful for power devices. [10][11][12][13] It has been known that the electron density of the AlGaN/GaN heterostructure increases with the thickness of Al x Ga 1−x N and Al mole fraction x. 14 In an endeavor to integrate the merits of these two material systems, there have recently been substantial studies on current transport from graphene to Al x Ga 1−x N/GaN heterostructure.…”