Question

The reverse saturation current of p--n diode

• A. depends on doping concentrations
• B. depends on diffusion lengths of carriers
• C. depends on the doping concentrations and diffusion lengths
• D. depends on the doping concentrations, diffusion length and device temperature

Hint:

Reverse saturation current increases rapidly with temperature because \(n_i\) increases exponentially with \(T\).

Answer 1

The Correct Option is D

Step 1: Recall expression of reverse saturation current.
Reverse saturation current is mainly due to minority carriers:
\[ I_s \propto n_i^2\left(\frac{D_p}{L_p N_D} + \frac{D_n}{L_n N_A}\right) \]
Step 2: Identify dependencies.
From this expression, \(I_s\) depends on:
(i) doping concentrations \(N_A, N_D\)
(ii) diffusion constants \(D_n, D_p\)
(iii) diffusion lengths \(L_n, L_p\)
(iv) intrinsic concentration \(n_i\)
Step 3: Role of temperature.
\(n_i\) strongly increases with temperature, so \(I_s\) increases sharply with temperature.
Step 4: Match with option.
Thus, it depends on doping concentration, diffusion length and temperature.
Final Answer:
\[ \boxed{\text{(D) depends on the doping concentrations, diffusion length and device temperature}} \]