Donor magnetic field separation

It is clear that the effective mass model must be modified in order to account for different chemical donors. The FTIR experiment monitors the n = 1 to n = 2 transition. For shallow donors in many of the III-V compounds the 2s and 2p states are degenerate for all practical purposes. The resolution is improved by applying a magnetic field. The magnetic field separates the orbital angular momentum states. The magnetic field also compresses the wave function which sharpens the transitions, it also separates transitions due to different chemical impurities ( ). 

Identification of residual and doped donors have been identified in expitaxial GaAs using the photolumines-cence technique in the presence of applied magnetic fields. Transitions occur between excited initial and final states of the neutral-donor-bound-exciton complexes. The magnetic field compresses the wave function which sharpens the optical transitions. The magnetic field also separates the different donors when viewed from the neutral-donor-bound-exciton transitions. These two effects make possible the identification of donors when the donor concentration is in the mid lOlScm" range. 

It would be desirable to identify the residual donors in GaAs from the transition involving an exclton bound to the first non-rigid-rotational state. The terminal state consists of the excited state (n = 2) of the electron on the donor. The observation of different residual donor species from this transition is made possible by performing the experiment in a magnetic field. The magnetic field produces two effects (a) It separates out states with different orbital angular momentum and (b) it compresses the wave function which sharpens the lines and separates the donors. 

It was shown by Fetterman et al. ( 4) that the separation between different chemical donors increased monotonlcally with magnetic field strength. In their case they were analyzing the donors by the FTIR technique. Since the exciton is very loosely bound to the donor in the photoluminescence scheme, a similar response might... 

Figure 3. Separation of the Si and S donors as a function of magnetic field is shown by the closed circles. The solid line is the theoretical curve of x, (0)1 as a function of magnetic field. The zero-field value of . is 0.43 cm. (Reproduced with permission from Ref. TA. CopyrigKV f983 American Physical Society.)...

---