Silicon Ion Implant Activation in β-(Al0.2Ga0.8)2O3

As gallium oxide-based heterojunction devices gain prominence, low-resistance contacts to aluminum gallium oxide material are of increasing importance for high performance and access to modulation doped layers. Here, the activation of ion-implanted silicon donors is investigated as a function of donor density from 5 × 10¹⁸ cm⁻³ to 1 × 10²⁰ cm⁻³, activation anneal duration from 6 s to 600 s, and activation temperature from 900°C to 1140°C. Importantly, ohmic behavior was achievable across a reasonably wide process window at moderate to high doping concentrations. Specific contact resistance of 1 × 10⁻³ Ω cm² and sheet resistance of 2.8 kΩ/□ were achieved for a 60 nm-deep 1 × 10²⁰ cm⁻³ box implant after activation at 1000°C for 6 s with standard Ti/Au contacts. Under these conditions, an activation efficiency of 7% was observed with Hall mobility of ~32 cm²/Vs. Furthermore, we demonstrate a Schottky diode formed of implanted material with a rectification ratio > 10⁶ and further confirm the Hall carrier density results using capacitance–voltage profiling analysis. Finally, we show the significant impact of anneal duration and the potential for deleterious over-annealing which reduces the active carrier density, mobility, and resultant material conductivity.