MOVPE Growth of CdTe on Si Substrates for Gamma Ray Detector Fabrication

High crystalline quality thick films of single crystal CdTe were grown directly on (211) Si substrates using MOVPE growth technique for gamma ray detector fabrication. A highest growth-rate of 65 mum/h was achieved at a substrate temperature of 600^degC. Films were monocrystalline as confirmed from the X-ray diffraction pattern. Results from the 4.2 K photoluminescence measurement showed films were of good crystalline quality. The gamma detector was fabricated in a p-CdTe/n-CdTe/n⁺-Si heterojunction diode structure, which exhibited clear rectifying behavior with a low value of room-temperature reverse bias leakage current, typically 0.11 muA/cm² at 100 V bias. The detector leakage current was reduced by three orders of magnitude from the room-temperature value at -30^degC. The detector clearly demonstrated its spectroscopy capability by resolving energy peaks from the ²⁴¹Am gamma isotope.