Question

3.15 High injection condition The Shockley equation for a pn junction under forward bias, as shown in Figure 3.16 (a), was derived by assuming low (weak) injection conditions, that is Pn(0) ะ Дрп(0) « nno Or Nd on the n-side. Show that when the injection is no longer weak, that is when p(0) oN, the applied voltage V reaches Vsi (strong injection) given by SI where Vh is the thermal voltage (kgT/e). Calculate V, and Vsi for a Si pn junction that has Na1018cm 3 and N,-1016 cm 3. Can you use the Shockley equation when V > ⅓? What happens when N-N? What is your conclusion? cm and

Answer 1

1.In the n type material, there are many electrons i.ec many donors. Therefore, the donor concentration of the PN junction (which is given) is almost equal to the donor concentration in the n type material

(b). Even in the reverse bias it is same.

2. The formulae for the In and Ip are there in the 4th question just substitute the values there in the formulae, we will get the ans.

3. In the question after solving the In and Ip and add both of the values, we will get the forward bias current.

4. V = T/ni