This part is a kind of semiconductor called FB31N20D.

Function of this product has IRFB31N20D.

Manufacturers : International Rectifier

Image and pinout :

Some of the text within the PDF file :

PD- 93805B SMPS MOSFET IRFB31N20D IRFS31N20D IRFSL31N20D HEXFET® Power MOSFET Applications l High frequency DC-DC converters VDSS 200V RDS(on) max 0.082Ω ID 31A Benefits Low Gate-to-Drain Charge to Reduce Switching Losses l Fully Characterized Capacitance Including Effective COSS to Simplify Design, (See App. Note AN1001) TO-220AB l Fully Characterized Avalanche Voltage IRFB31N20D and Current l D2Pak IRFS31N20D TO-262 IRFSL31N20D Absolute Maximum Ratings Parameter ID @ TC = 25°C ID @ TC = 100°C IDM PD @TA = 25°C PD @TC = 25°C VGS dv/dt TJ TSTG Continuous Drain Current, VGS @ 10V Continuous Drain Current, VGS @ 10V Pulsed Drain Current  Power Dissipation ‡ Power Dissipation Linear Derating Factor Gate-to-Source Voltage Peak Diode Recovery dv/dt ƒ Op [ ... ]

FB31N20D PDF Datasheet Download