Demonstration of near-ideal Schottky contacts to Si-doped AlN

Abstract

Near-ideal behavior in Schottky contacts to Si-doped AlN was observed as evidenced by a low ideality factor of 1.5 at room temperature. A temperature-independent Schottky barrier height of 1.9 eV was extracted from temperature-dependent I–V measurements. An activation energy of ∼300 meV was observed in the series resistance, which corresponded to the ionization energy of the deep Si donor state. Both Ohmic and Schottky contacts were stable up to 650 °C, with around four orders of magnitude rectification at this elevated temperature. These results demonstrate the potential of AlN as a platform for power devices capable of operating in extreme environments.

Over 600 V Lateral AlN-on-AlN Schottky Barrier Diodes with Ultra-Low Ideality Factor

“…It should be noted that the j eff is in good agreement with the predicted value for Ni Schottky contacts. 15,21) It is worth noting that previous high-voltage AlN SBDs [16][17][18][19][20] failed to demonstrate high j eff close to theoretical values due to deviation from the TE model. Figure 3(b) shows the temperature dependence of j eff and η of the devices.…”

“…4,13,14) Furthermore, Schottky contacts to AlN with ideal Schottky barrier heights (j b ) are difficult to achieve. 15) Recent studies on AlN Schottky barrier diodes (SBDs) have shown promising high-voltage electronic devices. [16][17][18][19][20] However, all these devices suffer from high ideality factors (η) >4.0, indicating the current transport mechanism deviates from the well-known thermionic emission (TE) theory.…”

“…First, the current due to TE is very low due to high j b (∼2 eV for Ni Schottky contacts). 15,21) Second, the current through defects and dislocations may be present at low-bias conditions which reduces the TE current. At high bias, the current transport is limited by the series resistance of the AlN epilayers.…”

“…At high bias, the current transport is limited by the series resistance of the AlN epilayers. Recently, Quiñones et al 15) demonstrated low η AlN SBDs (η = 1.5-1.7) with Ni Schottky contacts. They utilized large area rectangular ohmic contacts (∼few mm 2 ) to suppress the dislocation/defect-induced current to enhance the TE current.…”

“…This behavior has also been commonly observed in previous reports. 15,[18][19][20] Figure 4(a) shows the reverse breakdown measurements of the AlN SBDs under RT. The devices exhibited a BV of 640 V, and the breakdown was destructive at the device edges due to the electric field crowding effect.…”