Another app note from IXYS on P-Channel power MOSFET application. Link here (PDF)
IXYS P-Channel Power MOSFETs retain all the features of comparable N-Channel Power MOSFETs such as very fast switching, voltage control, ease of paralleling and excellent temperature stability. These are designed for applications that require the convenience of reverse polarity operation. They have an n-type body region that provides lower resistivity in the body region and good avalanche characteristics because parasitic PNP transistor is less prone to turn-on. In comparison with Nchannel Power MOSFETs with similar design features, P-channel Power MOSFETs have better FBSOA (Forward Bias Safe Operating Area) and practically immune to Single Event Burnout phenomena. Main advantage of P-channel Power MOSFETs is the simplified gate driving technique in high-side (HS) switch position.