Fabrication and Characterization of Gate-Last Self-Aligned AlN/GaN MISHEMTs With <italic>In Situ</italic> SiN_{<italic>x</italic>} Gate Dielectric

Abstract

This paper reports on the fabrication and characterization of gate-last self-aligned in situ SiN x /AlN/GaN MISHEMTs. The devices featured in situ grown SiN x by metal-organic chemical vapor deposition as a gate dielectric and for surface passivation. Selective source/drain regrowth was incorporated to reduce contact resistance. SiN x sidewall spacers and low-κ benzocyclobutene polymer (κ = 2.65) supporting layers were employed under the gate head to minimize the parasitic capacitance for high-frequency operation. The device with a gate length (L G ) of 0.23 μm exhibited a maximum drain current density (I DS ) exceeding 1600 mA/mm with a high ON/OFF ratio (I ON /I OFF ) of over 10 7 . The current gain cutoff frequency ( f T ) and maximum oscillation frequency ( f max ) were 55 and 86 GHz, respectively. In addition, the effect of temperature, from room temperature up to 550 K, on the dc and RF performances of the gate-last self-aligned MISHEMTs was studied.Index Terms-AlN/GaN, benzocyclobutene (BCB) planarization, gate-last self-aligned, high-temperature, in situ SiN x , MISHEMT, RF, source/drain (S/D) regrowth.

Gate-first process compatible, high-quality in situ SiN x for surface passivation and gate dielectrics in AlGaN/GaN MISHEMTs

“…This in situ process could prevent the as-grown GaN HEMT barrier layer from being exposed to ambient air, thus effectively eliminating the process-related contamination and damage. Meanwhile, the higher growth temperature and lower deposition rate could obtain better SiN x dielectric quality [7,8]. Nevertheless, limited thickness of the strained SiN x on AlGaN is a critical issue for realizing its fundamental benefits as expected [7].…”

AlN/GaN HEMTs with fmax Exceeding 300 GHz by Using Ge-Doped n++GaN Ohmic Contacts

“…A lot of efforts have been applied in HEMT fabrications for better device performance, including selective etching, , self-aligned gate, , source and drain regrowth, – etc. Among them, source and drain selective regrowth is valued for its low contact resistance in GaN HEMTs, which requires high electron concentrations and a flat surface.…”

High-performance HZO/InAlN/GaN MISHEMTs for Ka-band application

“…For high-speed device application, different dielectric materials (Al 2 O 3 [10][11][12][13][14][15][16][17][18][19], HfO 2 [20][21][22], SiN [23][24][25][26][27], SiO 2 [28], TiO 2 [29], MgCaO [30], ZnO [31], et al) have been investigated as the gate dielectric in GaN MISHEMTs. The relevant device performance, such as maximum drain current (I d,max ) of 2.4 A mm −1 [32], on/off current ratio (I ON /I OFF ) of 5 × 10 8 [30], transconductance (g m ) of 653 mS mm −1 [11], f T /f max of 190/300 GHz [20], and Johnson's figure-of-merit (JFOM) of 10.8 THz V [23] has been demonstrated.…”