Thermal stability of deep-level defects in high-purity semi-insulating 4H-SiC substrate studied by admittance spectroscopy

アドミッタンススペクトロスコピーを用いた高純度半絶縁性4H-SiC基板中の深い準位の熱安定性の研究

岩本 直也*; Azarov, A.*; 大島 武; Moe, A. M. M.*; Svensson, B. G.*

Iwamoto, Naoya*; Azarov, A.*; Oshima, Takeshi; Moe, A. M. M.*; Svensson, B. G.*

Thermal stability of deep level defects in high purity semi-insulating (HPSI) 4H-Silicon Carbide (SiC) substrates was studied. The samples were annealed from 700 to 1700 C, and Schottky barrier diodes (SBDs) were fabricated on the samples. The SBDs were characterized by current-voltage, capacitance-voltage and admittance spectroscopy measurements. The forward current of SBDs increased substantially with the increase of annealing temperature, while the reverse leakage current remained below 10 A. The capacitance of the samples annealed at 1400 and 1500 C was essentially zero at bias voltages between 0 and 10 V, but after 1600 and 1700 C annealing, the capacitance increased and started to respond to the bias voltage. The net hole concentrations in the 1600 and 1700 C annealed substrates were estimated to be 0.5110 and 1410 /cm, respectively. From admittance spectroscopy, five defect levels were detected. Defect peaks relating to boron acceptors increased although defect peaks with deep levels decreased with increasing annealing temperature. Therefore, it can be concluded that deep levels which act as compensation centers for boron acceptors dissociate by high temperature annealing, and as a results, hole concentration increases.