In this work, we review the novel growth technique developed at McMaster University involving He-plasma-assisted gas source molecular beam epitaxy (GSMBE) which produces III-V materials with properties useful in specific device applications. Using this technique, InP or InGaAsP (1.55 mu m) is grown under standard GSMBE conditions (for substrate temperature and source fluxes) except that the surface of the sample is exposed to He plasma particles produced with an electron-cyclotron resonance (ECR) source during growth. Undoped materials exhibit high resistivity and reduced carrier lifetimes. The quaternary material is of potential interest to the telecommunications industry, because it can be grown with a band-gap wavelength of 1.5 mu m and has exhibited sub-picosecond lifetimes when doped with Be. New results are reported on extensive van der Pauw Hall effect studies on the quaternary samples having various doping (Be or Si) and rapid thermal annealing conditions. By fitting the electrical data with a Fermi statistics model, four trap energy levels and concentrations have been identified.