Radio-Frequency (RF) losses on High-Resistivity Silicon (HRS) substrates were studied for several different surface passivation layers comprising thin-films of SiC, SiN and SiO₂ In many combinations, losses from conductive surface channels were reduced and increasing the number of interfaces between thin-films was found to be beneficial. In some cases the surface losses were completely eliminated. For example, with plasma-enhanced chemical-vapor deposition (PECVD) α-SiC layers up to a few tens of nm thick and exposed to nitridation or SiN growth at 850°C to form a SiC:N interface layer, values for the total losses of 1.6 dB/cm were achieved. Analysis of these layers was performed by using temperature dependent measurements of the RF losses on Coplanar Waveguides (CPWs), the capacitance-voltage characteristics and the sheet resistance along the Si surface. The overall results can be explained by assuming that the thin-films are so defected that they allow vertical current paths to highly-resistive interface layers where both fixed and mobile charge can be stored.

Pure gallium and pure boron (PureGaB) Ge-on-Si photodiodes were fabricated in a CMOS compatible process and operated in linear and avalanche mode. Three different pixel geometries with very different area-to-perimeter ratios were investigated in linear arrays of 300 pixels with each a size of 26 × 26 μm2. The processing of anode contacts at the anode perimeters leaving oxide covered PureGaB-only light-entrance windows, created perimeter defects that increased the vertical Ge volume but did not deteriorate the diode ideality. The dark current at 1 V reverse bias was below 35 μA/cm2 at room temperature and below the measurement limit of 2.5 × 10-2 μA/cm2 at 77 K. Spread in dark current levels and optical gain, that reached the range of 106 at 77 K, was lowest for the devices with largest perimeter. All device types were reliably operational in a wide temperature range from 77 K to room temperature. The spectral sensitivity of the detectors extended from visible to the telecom band with responsivities of 0.15 and 0.135 A/W at 850 and 940 nm, respectively.