GROWTH OF FULLY DOPED HG1-XCDXTE HETEROSTRUCTURES USING A NOVEL IODINE DOPING SOURCE TO ACHIEVE IMPROVED DEVICE PERFORMANCE AT ELEVATED-TEMPERATURES

Band gap engineered Hg1-xCdxTe (MCT) heterostructures should lead to d etectors tors with improved electro-optic and radiometric performance at elevated operating temperatures. Growth of such structures was acco mplished using metalorganic vapor phase epitaxy (MOVPE). Acceptor dopi ng with arsenic (As), using phenylarsine (PhAsH(2)), demonstrated 100% activation and reproducible control over a wide range of concentratio ns(1 x 10(15) to 3.5 x 10(17) cm(-3)). Although vapor from elemental i odine showed the suitability of iodine as a donor in MCT, problems aro se while controlling low donor concentrations. Initial studies using e thyliodide (EtI) demonstrated that this source could be used successfu lly to dope MCT, yielding the properties required for stable heterostr ucture devices, i.e.approximate to 100% activation, no memory problems and low diffusion coefficient. Cryogenic alkyl cooling or very high d ilution factors were required to achieve the concentrations needed for donor doping below approximate to 10(16) cm(-3) due to the high vapor pressure of the alkyl. A study of an alternative organic iodide sourc e, 2-methylpropyliodide (2 MePrI), which has a much lower vapor pressu re, improved control of low donor concentrations. 2 MePrI demonstrated the same donor source suitability as EtI and was used to control iodi ne concentrations from approximate to 1 x 10(15) to 5 x 10(17) cm(-3). The iodine from both sources only incorporated during the CdTe cycles of the interdiffused multilayer process (IMP) in a similar manner to both elemental iodine and As from PhAsH(2). High resolution secondary ion mass spectroscopy analysis showed that IMP scale modulations can s till be identified after growth. The magnitude of these oscillations i s consistent with a diffusion coefficient of approximate to 7 x 10(-16 ) cm(2)s(-1) for iodine in MCT at 365 degrees C. Extrinsically doped d evice heterostructures, grown using 2 MePrI, have been intended to ope rate at elevated temperatures either for long wavelength (8-12 mu m) e quilibrium operation at 145K or nonequilibrium operation at 190 and 29 5K in both the 3-5 mu m and 8-12 mu m wavelength ranges. Characterizat ion of such device structures will be discussed. Linear arrays of mesa devices have been fabricated in these layers. Medium wave nonequilibr ium device structures have demonstrated high quantum efficiencies and R(0)A = 37 Omega cm(2) for lambda(co) = 4.9 mu m at 190K.