Improved Power Device Figure-of-Merit ($4.0\times 10^{8}$ V$^{2}$ $\Omega^{-1}$ cm$^{-2}$) in AlGaN/GaN High-Electron-Mobility Transistors on High-Resistivity 4-in. Si

Abstract

The OFF-state breakdown voltage (BV gd ) characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) on a 4-in. Si substrate were investigated and analyzed. The HEMTs with L gd ¼ 10 m exhibited BV gd of 723 V with the specific on-resistance R DS½ON of 1.3 m cm 2 . Due to the improved ohmic contact, the devices exhibited low R DS½ON values. The power device figure-of-merit (FOM ¼ BV gd 2 =R DS½ON ) is as high as 4:0 Â 10 8 V 2 À1 cm À2 , the highest among the reported values for GaN HEMTs on a 4-in. Si. Due to the low vertical buffer leakage current, a high vertical breakdown voltage of $1200 V has been achieved with the total buffer thickness (d Buff ) of 2.2 m. # 2011 The Japan Society of Applied Physics I II-Nitride semiconductors are emerging as the best candidates for high-speed power switching devices. 1-7) Apart from AlGaN/GaN high-electron-mobility transistors (HEMTs) on SiC and sapphire, AlGaN/GaN HEMTs on Si substrate are emerging as the most suitable choice for commercialization due to their low cost and the availability of larger sizes even up to GaN on 6-in. Si 7) and 8-in. Si 8) substrates. Although the higher lattice-and thermalmismatches of Si generate a large number of dislocations and cracks, AlGaN/GaN HEMTs on Si have shown attractive device performance for high-power applications. 1,[4][5][6][9][10][11][12][13][14] Most high power switching devices require a high three terminal OFF-state breakdown voltage (BV gd ) with low specific on-resistance (R DS½ON ) values. To achieve high BV gd , researchers have tried increasing the buffer layer thicknesses, 1,4,5) using C-doped buffer GaN 11,12) or Fe-doped buffer GaN, 13) wide gate-drain spacing (L gd ), 2,10,11,15,16) incorporation of a field plate, 2,12) AlN passivation, 14) double heterostructure field-effect transistors, 6,16,17) and complete removal of the Si substrate. 18,19) The potential problem in increasing the buffer thickness (d Buff ) is the formation of large wafer bowing which is not good for the fabrication of devices using a conventional lithography process. Due to the double leakage path between the ohmic contact and the Si substrate, Visalli et al. realized that the field plate is limited to enhance the breakdown voltage at the L gd > 8 m. 17) To achieve a higher switching speed with a good power device figure-of-merit (FOM), the device structure should have a higher two-dimensional-electron gas (2DEG) mobility channel with low contact resistance (R c ). For high-power switching device applications, most research groups have used a conducting Si substrate for the fabrication of GaN HEMTs. Recently, we have demonstrated low R DS½ON with high FOM (¼ BV gd 2 =R DS½ON ¼ 2:0 Â 10 8 V 2 À1 cm À2 ) by implementing ohmic recess etching on AlGaN/GaN HEMTs on high-resistivity (HR)-Si (>10;000 cm) with a 1.2-nmthick AlN spacer layer. 15) Umeda et al. realized the boosting of BV gd in GaN HEMTs on an HR-Si substrate with channel stoppers. 20) In this study, we are reporting the improved OFF-state breakdown characteristics of AlGaN/...

Low specific ON-resistance and high Figure-of-merit AlGaN/GaN HEMTs on Si substrate with non-gold metal stacks

“…3(b)). The measured BV gd is almost equivalent to the BV gd values measured in the GaN HEMTs with gold-based ohmic contacts [8]. Figure 3 (b) shows R DS[ON] and FOM for the different L gd values.…”

“…Figure 1 shows the schematic cross-section of the fabricated HEMTs on Si substrate. For BV gd measurements, the gate bias was maintained at -5.0 V with Si substrate grounded [8]. The samples were immersed in Fluorinert TM (FC-40) to avoid any atmospheric surface flashover at the gate-drain region while BV gd measurements [8].…”

“…For BV gd measurements, the gate bias was maintained at -5.0 V with Si substrate grounded [8]. The samples were immersed in Fluorinert TM (FC-40) to avoid any atmospheric surface flashover at the gate-drain region while BV gd measurements [8]. Figure 2 shows (a) I DS -V DS and (b) transfer characteristics of AlGaN/GaN HEMTs.…”

“…HR-Si (111) substrate [7,8]. After the mesa isolation by BCl 3 /Cl 2 plasma, the samples went through ammonium sulphide [(NH 4 ) 2 S x ] surface treatment [9] and 120-nm thick SiN deposition by PECVD at 300 ºC.…”

Growth of compressively‐strained GaN films on Si(111) substrates with thick AlGaN transition and AlGaN superlattice buffer layers

“…To compete with the maturely used devices such as silicon MOS, IGBTs diodes, GaAs and SiC devices, and for GaNbased LED to compete with conventional lighting, GaNbased devices demand for large size and cheap substrates. At present, it seems that Si offers the great advantages because of its low cost, large diameter, high thermal conductivity and efficiency in processing [3].…”