Effect of gate structures on the DC and RF performance of AlGaN/GaN HEMTs

Abstract

This work analyzes the effect of various gate structures on the DC and radio frequency (RF) performance of AlGaN/GaN high-electron mobility transistors (HEMTs). AlGaN/GaN HEMT devices with a 3 μm drain-to-source spacing, 125 μm gate width and 0.3 μm gate length in various gate structures were fabricated to achieve the desired frequency response with a robust, high yield, and repeatable process. The maximum drain current (I DS , max), maximum DC transconductance (g m), pinch-off voltage (V th), current-gain cutoff frequency (f T), maximum oscillation frequency (f max), and RF characteristics of the devices in terms of the small-signal gain and RF output power (P out) at 8 GHz were investigated. The results showed that the output power is increased by 1 dB when the gate structure is changed from field plate to gamma gate. The V th , g m , f T and f max values are maximized when the thickness of the passivation layer between the gate foot and the gate head is minimized. It is shown that the I DS,max is decreased and P out is increased when the gate recess etching process is performed.

Selectively dry etched of p-GaN/InAlN heterostructures using BCI3-based plasma for normally-off HEMT technology

“…The p-GaN, InAlN and p-GaN/InAlN HEMT structure were grown on a 2′ Si substrate in a low-pressure metalorganic chemical vapor deposition reactor (Aixtron 200/4 RF-S). Trimethylgallium (TMGa), trimethylaluminum (TMAl), trimethylindium (TMIn), and ammonia (NH 3 ) were used as Ga, Al, In, and N precursors, respectively [12,13]. The growth of the all samples were initiated with a AlN nucleation layer and then an AlGaN buffer layer on it.…”

Optimization of Graded AlInN/AlN/GaN HEMT Device Performance Based on Quaternary Back Barrier for High Power Application

“…With 4um drain-source spacing, 0.8 um gate length is defined as reasonable and optimum for HEMTs. 39,40 Because beyond the optimum length of 0.8 um, the electric field under channel due to the gate does not have much effect but it does surges the ECS Journal of Solid State Science and Technology, 6 (12) P805-P812 (2017) P807 parasitic capacitance in particular the capacitance for gate-drain, leading to performance degradation. Hence the gate length was chosen to be 0.8 um.…”

Analysis of AlGaN/GaN HEMT and Its Operational Improvement Using a Grated Gate Field Plate

“…The cut-off frequencies f T and f max were calculated by extrapolation of current gain and unilateral power gain frequency plots at a slope of −20 dB/dec until the 0 dB line. 8,28,40 f T /f max for GFP (GGFP) HEMT is 17.6/44 (28.3/80) GHz depicting a 60% and 81% increase in cut-off frequencies of the proposed device, respectively. Some similar methodological work is also reported earlier in 13,21,29 where various gate structure configurations are studied for DC and RF performance, though with different gate lengths of 0.5 μm and 0.7 μm .…”

“…The wafer is then patterned for deposition of the metal Ni/Au gate using e-beam evaporation and a post-deposition anneal at 500 o C for 5 min followed by 50 nm silicon nitride passivation by plasma-enhanced chemical vapor deposition (PECVD). 28,29 The GGFP HEMT geometry is achieved after proper patterning and exposure through field plate/grated field plate mask where a conventional 1 μ m field plate attached to a gate is modified and grated (middle 0.6μ m removed such that L GFP = 0.2μm , L GGFP = 0.2μm ) to render GGFP HEMT geometry. 13 Finally, the contact opening is done for source/ drain contacts and the proposed design GGFP HEMT structure is obtained as shown in Fig.…”

“…We observe that the proposed grated gate field plate HEMT showcases better performance among these device gate structures. 13,25,28 In order to achieve higher f T and f max , high g m and smaller intrinsic parasitic capacitance are necessary where both the conditions are fulfilled by the GGFP HEMT device structure and presents a better alternative.…”