Scaling of bandgap reduction in heavily nitrogen doped GaAs
Abstract
The bandgap reduction caused by heavy impurity doping in a semiconductor can be written as δE_{g}(x)~x^{α}, where x is the mole fraction of the impurities, and α is the scaling exponent. It is well known that α=1/3 for n or ptype (i.e., charged) doping, where the isolated impurity center forms bound states. In contrast, the incorporation of isoelectronic impurities into a semiconductor commonly results in alloy formation. In this case, the impurities do not form any bound states (with small cluster sizes), and one finds that α=1. However, for the case of nitrogen doping in GaAs, although isolated nitrogen impurities do not form bound states, nitrogen impurity pairs do, and we find α=2/3. The scaling rule revealed here demonstrates that the dominant mechanism for the large bandgap reduction observed in GaAs_{1x}N_{x} is the formation of an impurity band associated with nitrogen pair bound states.
 Publication:

Physical Review B
 Pub Date:
 April 2001
 DOI:
 10.1103/PhysRevB.63.161303
 Bibcode:
 2001PhRvB..63p1303Z
 Keywords:

 71.55.Eq;
 78.20.Jq;
 IIIV semiconductors;
 Electrooptical effects