Reflection-mode quantum efficiencies have been calculated for the p-InP bias-assisted photoemitter (TE cathode) and have been found to be consistent with experimental data. The calculations, using Monte Carlo techniques, consider the transport of photogenerated electrons to the surface as well as the transmission of electrons at the surface into vacuum. Dependence of the predicted yield upon bias voltage and doping is discussed. Acceptor doping in the mid 1016/cm3 range is indicated as a good choice for a high quantum efficiency photocathode.
Vapor-phase epitaxial growth of In0.53Ga0.47As lattice matched to (100) -oriented InP substrates is described, and the performance of photodiodes fabricated from this material is presented. Gas-flow conditions for lattice-matched growth with various Ga-CHl flows were established for growth using the hydride process. The effect of substrate temperature on gas-flow ratios necessary for lattice-matched growth was studied over the temperature range 650–750 °C. Growth rates were found to vary from about 8 to about 60 μm/h over this temperature range. The activation energy of surface reaction was determined to be 44 kcal/mole. Photodiodes fabricated from an InP/In0.53Ga0.47As/InP structure showed rise and fall times of ≲1 nsec with quantum efficiencies in excess of 95% at 1.22 μm.
Thin films of boron nitride were grown by reactive plasma deposition using the ammonia‐diborane reaction. The crystalline growth on substrates of silicon, compression‐annealed pyrolytic graphite, and compression‐annealed pyrolytic
BN
was investigated by electron microscopy, and composition of the deposited material was determined by electron microprobe analysis. The effect of gas ratio and substrate temperature on growth rate was also investigated. Some crystalline order was observed; the largest single crystal
BN
grains were obtained on compression‐annealed pyrolytic graphite. Resistivities of the order of
2×109 normalΩ‐normalcm
were measured with dielectric constant varying from 2.7 to 7.7 for growth with different gas ratios. Efforts to determine the drift velocity of carriers in thin films of
BN
were not successful.
We report the temperature dependence of the incorporation of Ga during LPE growth of In0.53Ga0.47As on (111) B- and (100) -oriented InP substrates. The distribution coefficients of Ga can be accurately represented by KGa(111)B =6.40×10−6 exp(1.10/kT) and KGa(100)=5.02×10−13 exp(2.37/kT), which are equal at 629 °C. The difference in activation energies is the source of the ’’discrepancy’’ reported by Pearsall etal. that KGa(111)B<KGa(100) at 621 °C while from our results KGa(111)B≳KGa(100) at 650 °C.
Reflection-mode photoemission to a 2.1-μm threshold has been achieved from an externally biased Ag/p-In0.77Ga0.23As cathode. Quantum yield at 1.9 μm is 2×10−3 electrons per incident photon for 2.4-V bias and a cathode cooled to ∼125 K. The cathode was grown by vapor-phase epitaxy on a compositionally graded InAsP on InP (100) substrate using the hydride process.
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