Schottky Barrier Diode Optimization for a Low Voltage Power Converter

Optimun barrier height and impurity concentration for a power Schottky diode for maximizing rectifying efficiency are theoretically derived. For a low output voltage, 1.5 ~ 2 V as a DC-DC converter, the barrier height has an optimum value of about 17 times the thermal voltage and the impurity concentration has approximately 1 × 10¹⁶ cm^-3, for n-type silicon. Schottky diodes with some kinds of barrier metals, such as titanium, hafnium and zirconium were fabricated and applied to a forward mode 2 V 50 A DC-DC converter. Power loss and efficiency were investigated in comparison with control molybdenum diodes. Titanium and hafnium diodes reduced the power loss from 49 W to 37 W for main circuit total loss, which improved the efficiency from 67% to 73%, at package surface temperatures below 60°C. These diodes show better efficiency up to 85°C, compared with molybdenum diodes. Smaller heat sinks or cooling fins can be used because of those low loss characteristics.