Diffusion constant = Mobility*Thermal Voltage
*Where,Thermal voltage = T/11600*
From above equation it is clear that Diffusion constant should increase with rise of temperature as it is Directly Proportional to Thermal voltage. On other hand Mobility Decrease with rise of temperature because of high Kernel vibration with rise in temperature that will reduce Diffusion constant. I am not able to conclude Whether Diffusion constant should increase or decrease with temperature.