Semi-Insulating Silicon for Microwave Devices
The concept of fully encapsulated, semi-insulating silicon (SI-Si), Czochralski-silicon-on-insulator (CZ-SOI) substrates for silicon microwave devices is presented. Experimental results show that, using gold as a compensating impurity, a Si resistivity of order 400 kΩcm can be achieved at room temperature using lightly phosphorus doped substrates. This compares favourably with the maximum of ~180kΩcm previously achieved using lightly boron doped wafers and is due to a small asymmetry of the position of the two gold energy levels introduced into the band gap. Measurements of the temperature dependence of the resistivity of the semi-insulating material show that a resistivity ~5kΩcm can be achieved at 100°C. Thus the substrates are suitable for microwave devices working at normal operating temperatures and should allow Si to be used for much higher frequency microwave applications than currently possible.
M. Kittler and H. Richter
D. M. Jordan et al., "Semi-Insulating Silicon for Microwave Devices", Solid State Phenomena, Vols. 156-158, pp. 101-106, 2010