A semiconducting material has a band gap if 1 eV.Acceptor impurities are doped into it which create acceptor level 1meV above the valence band.Assume that the transition form one energy level to the otheris almost forbidden if kT is less than `1//50`of the energy gap.Also,if kT is more than twice the gap, the upper levels have maximum polution.The temperature of the semiconductor is increaased form 0K.The concentration of the holes increase with temperature and after a certain temperature it becomes approximately constant.As the tamperature is further increased the hole concentration again starts increasing at certain temperature, Find the order of the temperature range in which the hoel concentration remains approximately constant.

Explanation

Give Band gap `= 1ev`
Net band gap after doping
`= (1-10^(-3))eV = 0.999eV
According to the question ,
`KT_1 = (0.999)/(50)
`T_1 = (0.999)/(50xx8.62xx10^(-5))`
`= 231.78 = 231.0
for the maximum limit,
`KT_2 = 2xx0.999`
`T_2 = (2xx3xx10^(-3))/(8.62xx10^(-5))`
` = (2)/(8.62) xx 10^2 = 23.2`
Tempareture rangeis `(23.2-231.8)`.