Off-state drain leakage reduction by post metallization annealing for Al₂ O₃ /GaN/AlGaN/GaN MOSHEMTs on Si

Abstract

Impact of post metallization annealing (PMA) on the off‐state drain leakage (Ioff) for Al2O3/GaN/AlGaN/GaN metal‐oxide‐semiconductor high electron mobility transistors (MOSHEMTs) on Si has been investigated. After implementation of PMA at 500 °C for 10 min in N2 ambient, the Ioff can be reduced by three orders of magnitude compared to that without PMA. In consequence, a high on/off current ratio of 108 and a steep subthreshold slope of 71 mV/dec are achieved for the MOSHEMTs. The reduction of Ioff results from the suppression of source‐drain surface leakage through the interface between Al2O3 and GaN. The decrease of accumulation capacitance of the MOS capacitors (MOSCAPs) after 500 °C PMA suggests an oxidation process at the GaN surface during the high temperature annealing, which was confirmed by the increase of oxide layer thickness measured by transmission electron microscopy (TEM), and also the increase of GaO/GaN bond ratio at the Al2O3/GaN interface revealed by X‐ray photoelectron spectroscopy (XPS). These results suggest that the significant reduction of Ioff after 500 °C PMA can be attributed to partial surface oxidation of the GaN cap, which suppresses the conduction path at the Al2O3/GaN interface.

Thin-barrier heterostructures enabled normally-OFF GaN high electron mobility transistors

“…In this way, 2DEG can be restored in the access region only and the channel underneath the gate remains depleted. The ohmic contact is formed with conventional alloyed Ti/Al/Ni/Au metal layers and the gate contact is a Ni/Au stack [35].…”

Large‐scale quantification of aluminum in AlxGa1‐xN alloys by ToF‐SIMS: The benefit of secondary cluster ions

“…Al x Ga 1‐ x N‐based materials, as a kind of wide band‐gap III‐ V semiconductors, have attracted lots of attention . Energy‐band engineering of AlGaN/GaN quantum structures relies intensely on mole ratio of Al/Ga, which puts forward urgent requirements on precise composition measurement of such materials .…”

“…Al x Ga 1-x N-based materials, as a kind of wide band-gap III-V semiconductors, have attracted lots of attention. [1][2][3][4] Energy-band engineering of AlGaN/GaN quantum structures relies intensely on mole ratio of Al/Ga, which puts forward urgent requirements on precise composition measurement of such materials. [5][6][7] Reliable and also convenient depth quantification methods are needed to check Al content and distribution in Al x Ga 1-x N films in Al x Ga 1-x N-based devices.…”

Impact of gate electrode formation process on Al2O3/GaN interface properties and channel mobility

“…[2][3][4][5][6][7][8][9] In the GaN MIS structure, an interface state density (D it ) of more than 10 11 eV −1 cm −2 is often observed near the conduction band minimum (E C ). [10][11][12] In an n-channel MISFET, the Fermi level at the GaN surface (E Fs ) is close to E C during the on-state. Then, the interface states near E C are charged by capturing electrons.…”