[SOLVED] VE320 Intro to Semiconductor Devices Homework 8

Description

Exercise 8.1

The high-frequency C−V characteristic curve of a MOS capacitor is shown in Figure 1. The area of the device is 2×10⁻³ cm². The metal-semiconductor work function difference is ϕ_ms = −0.50 V, the oxide is SiO₂, the semiconductor is silicon, and the semiconductor doping concentration is 2 × 10¹⁶ cm⁻³.

• Is the semiconductor n or p type?
• What is the oxide thickness?
• What is the equivalent trapped oxide charge density?(d) Determine the flat-band capacitance.

Figure 1: Figure for Problem 8.1

Exercise 8.2

Consider the high-frequency C − V plot shown in Figure 2.

• Indicate which points correspond to flat-band, inversion, accumulation, threshold,and depletion modes.
• Sketch the energy-band diagram in the semiconductor for each condition.

Figure 2: Figure for Problem 8.2

Exercise 8.3

A p-channel MOSFET has the following parameters:        = 15,

and V_T = −0.4 V. Calculate the drain current I_D for

• V_SG = 0.8 V,V_SD = 0.25 V;
• V_SG = 0.8 V,V_SD = 1.0 V ;
• V_SG = 1.2 V,V_SD = 1.0 V; (d) V_SG = 1.2 V,V_SD = 2.0 V.

Exercise 8.4

Consider a p-channel MOSFET with the following parameters:  and W/L = 20. The drain current is 100µA with applied voltages of V_SG = 0, V_BS = 0, and

V_SD = 1.0 V.

• Determine the V_T
• Determine the drain current I_D for V_SG = 0.4 V,V_SB = 0, and V_SD = 1.5 V. (c) What is the value of I_D for V_SG = 0.6 V,V_SB = 0, and V_SD = 0.15 V?

Exercise 8.5

One curve of an n-channel MOSFET is characterized by the following parameters:

I_D(sat) = 2 × 10⁻⁴ A,V_DS( sat ) = 4 V, and V_T = 0.8 V (a) What is the gate voltage?

• What is the value of the conduction parameter?
• If V_G = 2 V and V_DS = 2 V, determine I_D.
• If V_G = 3 V and V_DS = 1 V, determine I_D.
• For each of the conditions given in (c) and (d), sketch the inversion charge density and depletion region through the channel.

Exercise 8.6

An NMOS device has the following parameters:                 n⁺poly gate, t_ox = 400˚A,N_a =

1015 cm−3, and cm−2.

• Determine V_T.
• Is it possible to apply a V_SB voltage such that V_T = 0 ? If so, what is the value of V_SB ?

Exercise 8.7

Draw the I_D − V_SD relationship for a p-type MOSFET at different gate voltages, assuming the source is grounded. Explain why there is the saturation region, and how the saturation point changes with different gate voltages.