Optical and electrical properties of silicon-implanted α-Al₂O₃

Abstract

We report on the optical and electrical properties of silicon-implanted c-plane and m-plane α-Al2O3 substrates. A 100 nm deep box profile with a silicon concentration of 3 × 1019 cm−3 was obtained by multiple-energy silicon implantation. Photoluminescence measurements showed that the concentration of oxygen-vacancy-related defects increased due to ion implantation and decreased by annealing at 1300 °C. The silicon-implanted c-plane and m-plane α-Al2O3 samples had a surface roughness of less than 1 nm after thermal annealing below 1300 °C in a nitrogen ambient. Current–voltage measurements of the silicon-implanted m-plane α-Al2O3 sample after annealing at 1300 °C showed 0.6 μA at a bias of 100 V.

Sn and Si doping of α-Al2O3 (10-10) layers grown by plasma-assisted molecular beam epitaxy

“…Recently, we achieved electrically conductive m-plane α-Al 2 O 3 substrates by Si implantation and post-thermal annealing at over 1300 °C in a N 2 ambient. 12) However, the resistivity was over 10 4 Ωcm at 623 K because the implantation technique entails an ion bombardment, forming compensation defects, and the Siimplanted Al 2 O 3 substrate included a high concentration of unintentionally incorporated N and C atoms, which can compensate electrons. 13) Development of α-Al 2 O 3 -based devices will require doped layers with defect and impurity concentrations lower than that of the donor concentration.…”

“…Some of the Al 2 O 3 :Si layers were annealed for 30 min at temperatures (T a ) between 1000 °C and 1600 °C under various conditions after pumping out the chamber to a high vacuum, 5 × 10 -4 Pa. For the electrical measurements, mesa isolation was carried out by reactive-ion etching using a 70 nm thick Ni mask. After removing the Ni mask using piranha (H 2 SO 4 :H 2 O 2 = 3:1) for 1 min, Ti (20 nm)/Au (50 nm) contacts were deposited using electron-beam evaporation, followed by sintering at 850 °C for 1 min in a N 2 ambient at 1 × 10 4 Pa. 12) Current-voltage (I-V ) measurements were conducted at room temperature in the atmosphere between two rectangular contacts with width of 50 μm and length of 100 μm by using a semiconductor analyzer (Agilent B1500A) with a minimum measurement resolution of 1 pA. Hightemperature I-V measurements and transfer length measurements (TLMs) from room temperature to 1150 K were conducted under ∼10 -4 Pa by using a source measure unit (Keysight B2902B) in the vacuum prober station. were conducted under ∼10 -4 Pa from 15 K to room temperature at the vacuum prober station and under ∼10 -3 Pa at room temperature to 1073 K. The temperatures were precisely monitored under the sample and on the sample cover by using two thermocouples and a measurement controller (Lake Shore M91).…”

“…For the resistivity measurements, a 3 × 3 μm 2 Van der Pauw pattern was formed on the Al 2 O 3 sample by etching the Si-doped region except for the channel and contact regions. 12) 3. Growth and thermal annealing of Sn-and Si-doped 2(c).…”

“…Here, we should note that a few H, C, N, and Si atoms in the Si-implanted α-Al 2 O 3 diffused at T a < 1500 °C in the N 2 ambient. 12) The RMS roughness of the surface annealed in high vacuum was less than 1 nm (Sect. I in supplementary data).…”

“…The current in the Al 2 O 3 layer at T a = 1400 °C was 73 μA at a bias of 100 V. The current fell dramatically at T a = 1500 °C, similar to the result for the Si-implanted Al 2 O 3 sample. 12) Surface morphologies of the Al 2 O 3 layers with [Si] = 4 × 10 18 cm −3 before and after annealing at T a between 1200 °C and 1600 °C are shown in Fig. 4.…”