Help finding electric field for phonon emission.

[Johnny_Sparx]

Hello, I seem to be having a problem with an assignment :

I need to calculate the electric field at which optical phonons will be emitted. Here's what I have been given:

1. Semiconductor with effective mass m=0.26*m0.
2. The optical phonon energy is 50 meV.
3. The mean scattering time is tau=10e-13 s at 300K.

There was a hint given in the assignment as well: "the total kinetic energy of an electron is the sum of hte thermal energy and the acquired energy from the field in the form of drift velocity."

Can I get some guidance here? I am reviewing my notes but some help would be appreciated. Thanks in advance.

 

[zhanhai]

an EM wave can interact with a phonon mode of the same frequency and wavevector. As I remember it, frequency of 10**13 sec. corresponds to phonon energy of 40meV.

I doubt if any crystal can have an optical phonon energy of 50 meV? that may be a good news for much higher Tc.