Assume an n-type GaAs has an energy gap between conduction band and valence band

Question

Assume an n-type GaAs has an energy gap between conduction band and valence band E_g=1.42ev. The reduced electron mass in the conduction band is about 0.06me and the reduced hole mass in the valence band is about 0.6me. Please finish the following questions: Assume the compound semiconductor GaAs is in the thermal equilibrium state at room temperature (T=300K), if the movable electron concentrations is 10^15 cm^-1, please find the hole concentration p_0 based on the energy gap value provided. Now assume that external electron-hole pairs are injected into this n-type GaAs semiconductor at a rate of 10^24/cm^3 per second and in the end, it reaches a new equilibrium state between the electron-hole pair generation and the recombination of the electron-holes. Assume the recombination parameter is 10^-10 cm^3/s. Please find the recombination lifetime of electron-holes in this GaAs semiconductor. Based on the calculation in (2), please find the steady-state excess concentration in this GaAs. Based on the above calculations, please find the concentrations of electrons and holes in the new equilibrium state of the GaAs. Assume at absolute zero degree, the new equilibrium is achieved with the same electron-hole injection in this GaAs, can you find the difference between the quasi-femi energy of the conduction band and valence band?

Explanation / Answer

It shows the top edge of the valence band, denoted by Ev, and the bottom edge of the conduction band, denoted by Ec. The difference between Ec and Ev is the bandgap energy or energy gap i.e.Eg = Ec– Ev.

1. hole concentration po= Nv e-(EF-EV)kT

where Nv=7.08 *1018 cm-1

EF - EV = kT ln (Nv/p )

so solving we get EF-EV = 0.22 eV

po = 7.08*1018 e-(0.22)*0.02586

po =7.03*1018

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

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