Contrast the electron and hole drift velocities through a 10 um (micro meter) layer of intrinsic silicon
across which a voltage of 5V is imposed. Let up = 480cm2/Vs and un=1350cm
To calculate the drift velocities of electrons and holes in a semiconductor material like silicon, you
can use the following formula:
vd = μ × E
​
Where:
vd is the drift velocity (in cm/s),
μ is the mobility of the charge carrier (in cm²/Vs),
E is the electric field (in V/cm).
​
In your case, a voltage of 5V is applied across a 10 µm thick layer of intrinsic silicon. First, let's
calculate the electric field:
E=
V
d
​
Where V
E=
= 5 V and d = 10 μm = 10−4 cm.
5V
10−4 cm
​
= 5 × 104 V /cm
Now, you can calculate the drift velocities for electrons (vd,n ) and holes (vd,p ) using their respective
​
mobilities (μn
​
​
= 1350 cm2 /V s for electrons and μp = 480 cm2 /V s for holes):
​
For electrons:
vd,n = 1350 × 5 × 104 cm/s = 6.75 × 107 cm/s
For holes:
vd,p = 480 × 5 × 104 cm/s = 2.4 × 107 cm/s
Therefore, the drift velocity of electrons through the 10 µm layer of intrinsic silicon is 6.75 ×
107 cm/s, while the drift velocity of holes is 2.4 × 107 cm/s.