In this paper, we report the results of controlling charge density in pseudomorphic high electron mobility transistor (PHEMT) growth with single and double Si delta -doping. Silicon delta -doping level and charge density were monitored by non-destructive tools such as photoluminescence (PL), photoreflectance (PR) and contactless electrical reflectance (CER), and destructive tools such as Hall-effect measurement and secondary ion mass spectroscopy (SIMS). Device performance results on single and double S-doping PHEMTs are also discussed.