DOPING OF GASB SINGLE-CRYSTALS

Gash single crystals (undoped and doped with indium, tellurium and nit rogen) were grown using the Czochralski technique without encapsulant in an atmosphere of flowing hydrogen and studied for etch pit density (EPD). It was found that dopants showed no influence on the average EP D in grown crystals because of the very low temperature gradients (abo ut 35 K cm(-1)) in our furnace. For undoped, Te- and In-doped GaSb the EPD profiles showed a rapid decrease along the growth direction, whil e that in the case of N-doped crystals increased. It is possible to ex plain this behaviour of N-doped crystals on the basis of the developme nt of stresses close to the solidification interface due to the increa sed nitrogen volatilization during the growth. The EPD in the middle p ortion of all the crystals investigated was of the order of 10(0)-10(1 ) cm(-2).