SCIENCE CHINA Information Sciences, Volume 61, Issue 6: 062402(2018) https://doi.org/10.1007/s11432-017-9198-1

## High-voltage trench-gate hole-gas enhancement-mode HEMT with multi-conduction channels

• AcceptedJul 26, 2017
• PublishedNov 20, 2017
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### Abstract

In this paper, we present a novel high-voltagelow on-resistance trench-gate (TG) hole-gas enhancement-mode (E-mode)high-electron mobility transistor (HEMT) with multi-conduction channels(MCs) and investigate its mechanism using simulations. This device featuresa repetitive AlN/GaN hetero-junction unit and a GaN/Al$_{0.26}$Ga$_{0.74}$Nhetero-junction. Its source and drain are located on the same side of themetal-insulator-semiconductor (MIS) TG, and the source is located besidethe gate. During operation, first, 2-D electron gas (2DEG) forms MCs atmultiple AlN/GaN hetero-interfaces. These MCs result in ultra-low specificon-resistance ($R_{\rm~on,sp})$ and improved transconductance ($g_{\rm~m})$. Second, 2-Dhole gas (2DHG) is induced at the GaN/Al$_{0.26}$Ga$_{0.74}$Nhetero-interface to prevent electrons from being injected from the source tothe MCs. As such, E-mode operation is realized, which exceeds theperformance of the conventional E-mode method by depleting the 2DEG underthe gate. Third, in the off-state, 2DHG and 2DEG are depleted into negativeand positive charges, respectively, thereby forming the polarizationjunction. This depletion region is extended due to the electric field(E-field) modulation effect by the polarization junction, thereby achievingan enhanced breakdown voltage (BV). Fourth, the drain-induced barrier lowering(DIBL) effect is significantly suppressed, which ensures a high BV and lowleakage current. Additionally, due to the unique source location, theTG-MC-HEMT is smaller than the conventional MIS AlGaN/GaN HEMT (Con-HEMT).The BV of the TG-MC-HEMT is 604 V and the $R_{\rm~on,sp}$ value can be as small as0.38 m$\Omega~\cdot~$cm$^{2}$.

### Acknowledgment

This work was supported in part by National Natural Science Foundation of China (Grant No. 51677021) and Fundamental Research Funds for the Central Universities (Grant No. ZYGX2014Z006).

• Figure 1

(Color online) Three-dimensional schematic of the proposed TG-MC-HEMT.

• Figure 2

(Color online) Electron density distributions of TG-MC-HEMT ($n=2$) at (a) $V_{\rm~g}$ = 0 V and (b) $V_{\rm~g}$ = 4 V.

• Figure 3

(Color online) Extracted hole and electron concentrations along the gate sidewall. (a) $V_{\rm~g}$ = 0 V; (b) $V_{\rm~g}$ = 4 V.

• Figure 4

(Color online) Conduction band profile along the gate sidewall at different $V_{\rm~g}$.

• Figure 5

(Color online) 2-D equipotential potential lines distribution of (a) TG-MC-HEMT ($n=1$), (b) TG-MC-HEMT ($n=2$), (c) Con-HEMT at breakdown.

• Figure 6

(Color online) Comparison of the $X$-component of E-field ($E_{X})$ and $Y$-component of E-field ($E_{Y})$ distributions of TG-MC-HEMT and Con-HEMT, ($y=0.22~\mu~$m).

• Figure 7

(Color online) Transfer characteristics curves at $V_{\rm~d}=~$ 0.5 V.

• Figure 8

(Color online) I-V output characteristic curves with $V_{\rm~g}$ = 4 V.

• Figure 9

(Color online) Off-state leakage current distribution with different $L_{\rm~g}$ (one order of magnitude/contour).

• Figure 10

(Color online) Conduction band profiles (a) TG-MC-HEMT for $n=2$ at 2DHG channel. Two source labels indicate two cases of $L_{\rm~g}=0.5~\mu~$m/1.5 $\mu~$m, respectively. (b) Con-HEMT at 2DEG channel. (c) Conduction band profile at 2DHG channel with different $T_{\rm~g}$ in the TG-MC-HEMT.

• Figure 11

(Color online) Dependence of the BV and $R_{\rm~on,sp}$ on the $L_{\rm~g}$.

• Figure 12

(Color online) Influence of the $N_{\rm~s}$ on $V_{\rm~th}$ and transfer curves as a function of $N_{\rm~s}$.

• Figure 13

(Color online) Conduction band profile along the $y$-direction as a function of $N_{\rm~s}$.

• Figure 14

(Color online) $R_{\rm~on,sp}$ and BV in the proposed devices and recently reported AlGaN/GaN HEMTs, together with the theoretical Si-, SiC-, and GaN- limits.

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