The Semiconductor Research Group in Engineering at the University of Glasgow has pioneered MEMS gravimeters, Ge on Si single photon avalanche diode (SPAD) photodetectors and heterogeneously integrated photonic integrated circuits (PICs), lasers and MEMS vapour cells for chip-scale atomic systems. The group has demonstrated DFB lasers for quantum technologies / atomic systems with sub-4 kHz linewidths. The quantum technology chip-scale atomic systems being developed include optical atomic clocks, cold atom inertial sensors (accelerometers and gyroscopes), optically pumped magnetometers, co-magnetometer gyroscopes and electric field sensors. Both Ge on Si SPADs and Ge on Si avalanche photodiodes are being developed for quantum technology, range-finding, single-photon LiDAR and telecomms applications. The group made the first MEMS gravimeters with applications in PNT, geophysics, geodesy, energy, security, defence and environmental monitoring which are now copied globally and have spun out the company Quantrologee to commercialise the technology.