First RF Power Operation of AlN/GaN/AlN HEMTs With >3 A/mm and 3 W/mm at 10 GHz

Abstract

The AlN/GaN/AlN heterostructure is attractive for microwave and millimeter-wave power devices due to its thin top barrier, tight carrier confinement, and improved breakdown voltage. This work explores the large-signal RF performance of high-electron-mobility transistors on this heterostructure. Results are highlighted by record high on-current of 3.6 A/mm, and record maximum oscillation frequency (fmax) of 233 GHz. The load-pull power sweep at 10 GHz demonstrate a peak power added efficiency (PAE) of 22.7% with an associated gain (GT) of 8.7 dB and output power (Pout) of 3 W/mm. When optimized for power, the peak Pout of 3.3 W/mm has an associated PAE of 14.7% and GT of 3.2 dB. This first demonstration is encouraging for the mm-wave power potential of the AlN/GaN/AlN HEMT.

In Situ Crystalline AlN Passivation for Reduced RF Dispersion in Strained‐Channel AlN/GaN/AlN High‐Electron‐Mobility Transistors

“…In particular, recent AlN HEMTs on SiC [ 4,20,21 ] have made giant strides toward fulfilling the promise of high‐mm‐wave output powers at frequencies upto 94 GHz. They have shown good direct current (DC) characteristics with high on‐currents of 3 A mm −1 and small‐signal characteristics with f T / f MAX of 123/233 GHz.…”

“…The state‐of‐art‐scaled T‐gate AlN/GaN/AlN HEMTs on SiC have demonstrated output powers of 3.3/2.2 W mm −1 at 10/94 GHz, respectively, without field plates. [ 20,21 ] In addition, AlGaN/GaN/AlN HEMTs on single‐crystal AlN substrates recently demonstrated phenomenal 15 W mm −1 in the X‐band, [ 4 ] further demonstrating the potential of this platform for high‐power amplification. Although these results are remarkable for device technology early in its development stage, they are still below the state‐of‐art GaN HEMTs’ output powers of upto 8 W mm −1 at 94 GHz.…”

“…Although these results are remarkable for device technology early in its development stage, they are still below the state‐of‐art GaN HEMTs’ output powers of upto 8 W mm −1 at 94 GHz. [ 6,22,23 ] It was found [ 21 ] that the DC‐RF dispersion due to surface states is what limits the capability of the current generation of AlN HEMTs to truly achieve its potential.…”

2DEG enhancement via epilayer stress engineering in AlN/GaN/AlN heterostructure

“…The SiC exists in several crystal structures, among which the 4H-SiC and 6H-SiC have the same space group as III-nitrides [38]. Despite their high prices, SiC substrates are extensively used for III-nitrides for performance-driven applications [37,[49][50][51][52][53][54]. The most attractive property of SiC is the low lattice mismatch and relatively lower thermal mismatch to GaN and AlN compared to sapphire and Si substrates [34,55,56].…”

“…The increase in the GaN channel thickness resulted in an increase in 2DEG density and carrier mobility. The AGA structure with 7 nm thick AlN barrier and 60 nm thick GaN channel layers showed a 2DEG concentration of 4.98×10 13 cm -2 and carrier mobility of 499 cm 2 V -1 s -1 which gives a state-ofthe-art µ×ns product of 2.485×10 16 V -1 s -1 [15,28,35,36,[49][50][51].…”