{"id":3358,"date":"2011-07-05T20:48:59","date_gmt":"2011-07-05T20:48:59","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/?p=3358"},"modified":"2011-07-19T20:28:45","modified_gmt":"2011-07-19T20:28:45","slug":"1-8-kv-breakdown-algangan-hemt-on-si-substrate","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/1-8-kv-breakdown-algangan-hemt-on-si-substrate\/","title":{"rendered":"1.8-kV-breakdown AlGaN\/GaN HEMT on Si Substrate"},"content":{"rendered":"

The combination of high critical electric field, carrier mobility and thermal stability makes GaN an ideal semiconductor for power switches [1<\/a>] <\/sup>. Additionally, the growth of GaN-based semiconductors on large area Si substrates significantly reduces the cost of these devices and enables their fabrication in state-of-the-art Si fabs. This paper demonstrates a GaN-on-Si HEMT with a 1.8-kV breakdown voltage and a record 2.4 m\u03a9,cm-2. specific on resistance.<\/p>\n

The devices were fabricated on an AlGaN\/GaN heterostructure grown on a 4-in Si substrate by MOCVD. The fabrication process began with plasma etching for device isolation; then a Ti\/Al\/Ni\/Au metal stack was deposited on the source and drain contact region, followed by an 870\u00b0C rapid thermal annealing to form the ohmic contacts. Two-micron-long gate electrodes were deposited using Ni\/Au\/Ni. The devices have a gate-to-source distance of 1.5 \u03bcm and gate width of 100 \u03bcm. The gate-to-drain distance L-gd. varies from 5 <\/em>\u03bcm to 35 \u03bcm.<\/p>\n

Breakdown voltage measurements were carried out at a gate voltage Vg.=\u22128 V and with the samples immersed in Fluorinert to avoid surface flashover through air. The breakdown voltage Vbr. was defined as the voltage when the drain-to-source leakage current density I-D. exceeded 1 mA\/mm. The breakdown voltage of the devices increases linearly with Lgd at a rate of 140 V\/\u03bcm (Figure 1). However, the breakdown voltage saturates at Lgd.=12 \u03bcm due to vertical leakage through the Si substrate [2<\/a>] <\/sup>. The maximum current density for a device with Lgd=12 \u03bcm is 375 mA\/mm. Figure 2 shows the specific on resistance of the devices fabricated in this work as a function of breakdown voltage. This performance makes these devices very promising for power electronic applications including electric vehicles and photo-voltaic power inverters. Even higher breakdown voltage could be achieved by removing the substrate [2<\/a>] <\/sup>; this goal is the focus of our on-going work.<\/p>\n\n\t\t