The band gap of the semiconductor gallium arsenide (GaAs) is 1.43 eV , and the b

Question

The band gap of the semiconductor gallium arsenide (GaAs) is 1.43 eV , and the bandgap for the semicondcutor aluminum gallium arsenide (AlGaAs) is 2.06 eV.

a) What is the maximum wavelength absorbed by GaAs?

b) What is the maximum wavelength absorbed by AlGaAs?

c) A CD player and a DVD player use a semiconductor diode laser to read data off a CD or DVD disc respectively. The capacity of a CD is 650 MB and the capacity of a DVD disc is 8 GB. Which semiconductor (GaAs or AlGaAs) is used in the DVD player? Explain your answer based on the capacity of the CD and DVD, and that the area of the CD and DVD are the same (assuming both are single layer).

d) A blue ray disc has a capacity of 25 GB. What is blue about the blue-ray player?

Explanation / Answer

a) l=hc/E= 1240eV.nm/1.43eV = 867.13nm

b) l=hc/E= 1240eV.nm/2.06eV = 601.94 nm

c) The CD and the DVD have the same size, but the DVD has more capacity. Therefore, a DVD player needs to be able to read smaller features than a CD player. A DVD player uses the semicondictor that absorbs shorter wavelenghth. --> AlGaAs

d) Blu-ray player uses GaN based blue lasers. GaN's band gap is around 3eV.

l=1240eV.nm/3eV=413.33nm, which approximately is the wavelength of blue visible light.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.