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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 600degC. 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 -30degC. The detector clearly demonstrated its spectroscopy capability by resolving energy peaks from the 241Am gamma isotope.