Recent advances in semiconductor optoelectronics and electronics based on wide band-gap nitride materials have resulted in substantial interest in the basic properties of wurtzite crystals.Particularly

acomplete understanding of carrier-phonon interaction mechanisms and rates is essential to further progress in these fields.There are many more distinct phonon branches (nine optical and three acoustic modes) in wurtzite mate-rials.At the same time the phonon modes may not be purely longitudinal nor transverse modss.Since B.C. Lee presents a theory of electron-optical-phonon interaction in uniaxial crystals of wurtzite type based on the macroscopic dielectric continuum model and the uniaxiaal models

the special properties of superlattice and beterostructure have been investigated by many persons.However the effect of the external magnetic field on the nitride parabolic quantum well materials

to our knowledge

have rarely been investigated. In this paper

the energy level of a free polaron in a nitride infinite parabolic quantum well as function of the external magnetic field is studied using the LLp variational method.The ground state energy of polaron changing with the width of the quantum well and the external magnetic fields are obtained.Our numerical resuits for a GaN/Al

0.3

Ga

0.7

N parabolic quantum well show that the effects of the external magnetic fields on the ground state enerygy are very obvious.The energy of the polaron decrease with increasing well width and in-crease with increasing magnetic fields strength.At the same time

the contribution of the interaction between the electron and phonon to the energy of polaron in the nitride parabolic quantum well is noticeable.