Studies on electron beam evaporated ZrO₂/AlGaN/GaN metal–oxide–semiconductor high‐electron‐mobility transistors

Abstract

Metal–oxide–semiconductor high‐electron‐mobility transistors were demonstrated on AlGaN/GaN with electron beam (EB) evaporated ZrO2. The composition of the EB deposited ZrO2 thin films was confirmed using X‐ray photoelectron spectroscopy (XPS). The fabricated ZrO2‐based MOSHEMTs exhibited high positive gate voltage of operation up to +7 V with low gate leakage current. For a comparison, conventional high‐electron‐mobility transistors (HEMTs) were also fabricated with identical device dimensions. The maximum drain current densities of 1168 and 538 mA/mm were observed on MOSHEMTs and HEMTs, respectively. Low gate leakage current density of four orders of magnitude was observed on ZrO2‐based MOSHEMTs when compared with the conventional HEMTs. The observation of high forward on‐voltage with low gate leakage current density and high positive operational voltage reveals the importance of ZrO2 dielectric films for MOSHEMT devices. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reduction of current collapse in AlGaN/GaN MISHEMT with bilayer SiN/Al2O3 dielectric gate stack

“…The observation of high current collapse and gate leakage in Conv. HEMTs is due to the presence of a high interface trap density of ~1×10 13 cm −2 eV -1 at the Schottky gate/GaN interface which was determined using Eq. (2) [23],…”

“…Secondly, the high gate leakage currents that the conventional GaN HEMTs with Schottky metal gates suffer from, that limits the gate voltage swing and thus affecting the maximum output power as well the microwave performance [4,5]. To reduce the gate leakage currents, researchers have tried various gate dielectrics such as SiO 2 [6,7], SiN [8,9], Al 2 O 3 [10], MgO [11], Sc 2 O 3 [12], and ZrO 2 [13]. Among these, the atomic layer deposited (ALD) Al 2 O 3 is one of the most preferred gate dielectric schemes for GaN MISHEMTs [14][15][16][17] with its additional advantages such as wide band gap energy (9 eV), large dielectric constant (k ~ 10), high breakdown field (~10 MV/cm), high thermal and chemical stability.…”

AlGaN/GaN MISHEMTs with AlN gate dielectric grown by thermal ALD technique

“…This effect is also described as dynamic behavior degradation, gate lag, drain lag, etc., which is caused by the charge trapping effect on the AlGaN surface especially in the access region between gate and drain [4][5][6]. In order to solve these two issues, the deposition of oxide-based dielectric such as SiO 2 [7], Al 2 O 3 [8], LaLuO 3 [9], and SrO 2 [10,11] and dielectric stack such as SiN/Al 2 O 3 [12] as gate dielectric layer and passivation layer in the access region simultaneously is widely adopted. But it has been revealed that the introduction of oxide-based dielectric is likely to form Ga-O bond which is thought as one of interface sources leading to current collapse [13].…”

Off‐state drain current and breakdown voltage of AlGaN/GaN MIS‐HEMT with multilayered gate insulator

“…Thus, when the thickness of SiO 2 is increased in order to decrease the gate leakage current, the gate capacitance becomes low. The efficiency of controlling the carrier density in the channel by the gate voltage is lowered, and the gain of the HEMT worsens with increasing SiO 2 thickness.Recently, MIS-HEMTs using high-k material as the insulating film have been reported [4][5][6][7]. The high-k insulation film can be thickened without reducing the gain of the HEMT.…”