###### Solid State Electronic Devices

34 SOLVED PROBLEMS

Question: 4.3

## As a numerical example, let us assume that 10^13 EHP/cm³ are created optically every microsecond in a Si sample with n0 = 10^14 cm^-3 and τn = τp = 2 μs. The steady state excess electron (or hole) concentration is then 2 × 10^13 cm^-3 from Eq. (4–14). ...

While the percentage change in the majority electr...
Question: 8.1

## For steady state optical excitation, we can write the hole diffusion equation as Dp d²δp/dx²=δp/τp – gop Assume that a long p^+ – n diode is uniformly illuminated by an optical signal, resulting in gop EHP/cm³-s. Calculate the hole diffusion current Ip(xn) and evaluate it at xn = 0. Compare ...

\frac{d^2\delta p}{dx_n^2}=\frac{\delta p}{...
Question: 7.4

## A symmetrical p^+-n-p^+ bipolar transistor has the following properties: Emitter Base A = 10^-4 cm² Na = 10^17 Nd = 10^15 cm^-3 Wb = 1 μm τn = 0.1 μs τp = 10 μs μp = 200 μn = 1300 cm² >V-s μn = 700 μp = 450 cm² /V-s (a) Calculate the saturation current IES = ICS. (b) With VEB = 0.3V and ...

In the base, p_n=n_i^2/n_n=(1.5 \times 10^{...
Question: 8.3

## What composition x of AlxGa1-xAs would emit red light at 680 nm? What composition of GaAs1-xPx? ...

The band gap E_g(eV)=1.24/\lambda(\mu m)=1....
Question: 5.5

## Assume a p^+-n diode is biased in the forward direction, with a current If. At time t = 0 the current is switched to -Ir. Use the appropriate boundary conditions to solve Eq. (5–47) for Qp(t). Apply the quasi-steady state approximation to find the storage delay time tsd. ...

From Eq. (5–47), i(t)=\frac{Q_p(t)}{\tau_p}...
Question: 5.4

## An abrupt Si p-n junction (A = 10^-4 cm²) has the following properties at 300 K: p side n side Na = 10^17 cm^-3 Nd = 10^15 τn = 0.1 μs τp = 10 μs μp = 200 cm² /V – s μn = 1300 μn = 700 μp = 450 The junction is forward biased by 0.5 V. What is the forward current? What is the current at a ...

I=qA\Big(\frac{D_p}{L_p}p_n+\frac{D_n}{L_n}...
Question: 5.1

## An abrupt Si p-n junction has Na = 10^18 cm^-3 on one side and Nd = 5 * 10^15 cm^-3 on the other.(a) Calculate the Fermi level positions at 300 K in the p and n regions.(b) Draw an equilibrium band diagram for the junction and determine the contact potential V0 from the diagram.(c) Compare the ...

(a)  E_{ip} -E_{F} =kT\ln \frac{P{p} }{n_{i...
Question: 5.7

## For heterojunctions in the GaAs–AlGaAs system, the direct (Г) band gap difference ΔE^Γg is accommodated approximately 2/3 in the conduction band and 1/3 in the valence band. For an Al composition of 0.3, the AlGaAs is direct (see Fig. 3–6) with ΔE^Γg = 1.85 eV. Sketch the band diagrams for ...

Taking  ΔE_{g} = 1.85 - 1.43 = 0.42 [/latex...
Question: 5.3

## Find an expression for the electron current in the n-type material of a forward-biased p-n junction. ...

The total current is I=qA\left(\frac{D_{p} ...