ELECTRICAL-PROPERTIES OF HEAVILY CARBON-DOPED GAAS EPILAYERS GROWN BYATMOSPHERIC-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION USING CBR4

Heavily carbon (C)-doped GaAs epilayers with hole concentrations as hi gh as 3.1 x 10(20) cm(-3) were grown by atmospheric pressure metalorga nic chemical vapor deposition using CBr4 as the dopant source. The ele ctrical properties of C-doped GaAs epilayers simultaneously grown on e xact and 2 degrees off (100) GaAs substrates were investigated. The ho le concentration in the epilayer grown on the exact (100) substrate wa s higher than that in the epilayer on the 2 degrees off (100) substrat e grown under equivalent conditions. The hole concentration for the ex act (100) substrates exhibited saturation as the growth temperature in creased. The hole concentration for the 2 degrees off (100) substrates exhibited thermal activation behavior. The activation energy of the h ole concentration as a function of the growth temperature did not chan ge significantly regardless of the V/III ratio (E(a) similar to 63 and 71 kcal/mol). The higher desorption rate of C-containing species due to the higher adsorption rate of AsHx species on the 2 degrees off (10 0) substrate; which has a higher step density than the exact (100) sub strate, is responsible for this thermal activation behavior.