Nitrogen-induced increase of the maximum electron concentration in group III-N-V alloys

The maximum free-electron concentration is observed to increase dramatically with the nitrogen content x in heavily Se-doped Ga1-3xIn3xNxAs1-x (0 less than or equal to x<0.033) films. For example, an electron concentration of 7 x 10(19) cm(-3) was observed at x=0.033; a value more than 20 times larger than that observed in GaAs films grown under similar conditions. It is shown that the increase is caused by a combination of two effects: (1) a downward shift of the conduction band and (2) an increase of the electron effective mass caused by flattening of the conduction-band minimum. Both these effects are due to modifications td the conduction-band structure caused by an anticrossing interaction of a localized N state and the conduction band of the III-V host.