R. L. Moon

Bandgap and lattice constant of GaInAsP as a function of alloy composition

AbstractPublished data for the composition dependence of the room-temperature bandgap (Eg) and lattice constant (ao) in the pseudobinary GayIn1-yAs, GayIn1-yP, GaAsxPl-x, and InAsxPl-x systems have been used to derive the following equations for the quaternary GayInl-yAsx Pl-x, alloys:

Dependence on Crystalline Face of the Band Bending in Cs2 O‐Activated GaAs

\begin{gathered} a_o ({\AA}) = 5.87 + 0.18x - 0.42y + 0.02xy \hfill \\ E_g (eV) = 1.35 - x + 1.4y - 0.33xy - (0.758 - 0.28x)y(1 - y) \hfill \\ - (0.101 + 0.109y) x(1 - x). \hfill \\ \end{gathered}

The organometallic VPE growth of GaAs1−ySby using trimethylantimony and Ga1−xInxAs using trimethylarsenic

Available experimental data are in excellent agreement with these equations.

Organometallic‐sourced VPE AlGaAs/GaAs concentrator solar cells having conversion efficiencies of 19%

For terrestrial applications, the figure of merit for photovoltaic solar energy conversion devices is watts output per dollar of cost. AlGaAs/GaAs heterojunction cells have a very favorable watts per dollar figure of merit when used at high values of sunlight concentration. An experimental 1/2−in.−diam cell was operated in air mass 1.4 sunlight with an output power density of 4.52 W/cm2 at an effective concentration of 312 suns with a power conversion efficiency of 17.5%. The same cell was operated at 200 °C with an output power density of 3.45 W/cm2 at a 14% efficiency. The efficiency of the cell was 23% with a fill factor of 0.85 at a lower concentration ratio which is obtainable using simple concentrator schemes.

Photoemission from cesium‐oxide‐activated InGaAsP

Electron energy loss in the band‐bending region of the p‐type III–V semiconductor in a III–V photocathode is an important factor in determining the escape probability and the optimum doping. From measurements of photoelectric yield near threshold from Cs2O‐activated n‐type GaAs, the position of the Fermi level at the GaAs–Cs2O interface was determined for {110}, {100}, {111A}, and {111B} surfaces. Assuming the Fermi‐level position at the GaAs surface to be independent of doping, the band bending for p‐type GaAs is greatest for the {111A} face and least for the {111B} face. The measured escape probabilities of photoexcited electrons from different crystalline faces of optimally activated 5 × 1018/cm3 Zn‐doped liquid epitaxial GaAs correlate well with the band‐bending measurements. The {111B} sample has an escape probability of 0.489 and a luminous sensitivity of 1837 μA/lm.

Characterization of organometallic VPE grown GaAs and AlGaAs for solar cell applications

A method of obtaining efficient photoemission in the wavelength region from 1 to 2 μm, using the transferred‐electron effect in a p ‐type semiconductor, is proposed. Experimental demonstration of emission from InP in this mode is reported.

Interfacial Barrier Effects in III‐V Photoemitters

The organometallic vapor phase epitaxial growth of Ga1−xInxAs and GaAs1−ySby using trimethylarsenic and trimethylantimony as the Group V sources is reported and the relevant chemistry is discussed. Growth rate and composition variations as a function of temperature are given for GaAs1−ySby. A result of particular importance is that no detrimental room temperature gas phase reaction is observed between triethylindium and trimethylarsenic. Consequently, the growths are performed at one atmosphere pressure without the need for any complicated injection schemes in the reactor design.

Performance of an Al0.92Ga0.08As/Al0.14Ga0.86As solar cell in concentrated sunlight

AlGaAs/GaAs heterojunction solar cells having conversion efficiencies greater than 19% have been produced on large‐area substrates (13 cm2) using the organometallic‐sourced VPE process. At 1 sun (simulated AM2) these devices have open‐circuit voltages of 1.01 V and short‐circuit currents of 20.9 mA/cm2. In sunlight at a flux concentration of 933 suns at AM2.1, a conversion efficiency of 19% and a fill factor of 0.757 was measured.