Szutsun Simon Ou

Gain‐ and threshold‐current dependence for multiple‐quantum‐well lasers

A semilogarithmic expression that accurately approximates gain‐current curves of quantum‐well lasers and is useful for optimization of device performance is derived. The derivation uses both a curve fitting of the calculated curves and approximate analytical evaluation of integrals that comprise the gain model. The derived expression is used to explain the observed increase in the threshold current of single‐ and multiple‐quantum‐well lasers.

Type conversion, contacts, and surface effects in electroplated CdTe films

Efficient electroplated CdS/CdTe solar cells can be fabricated by heat treating and type‐converting the n‐CdTe films deposited on CdS layers. In this paper, various mechanisms which may give rise to the conversion of electroplated CdTe films from n to p type are investigated. It is concluded that Cd‐vacancy generation is the main mechanism of type conversion. Possible effects of oxygen on this mechanism are also discussed. Evaporated Au contacts to electroplated p‐CdTe films were studied. It was found that the Au contacts depleted the excess Te present on the surface of Br2‐methanol etched p‐CdTe films. Oxygen was found to affect the electrical characteristics of such contacts.

Current transport mechanisms of electrochemically deposited CdS/CdTe heterojunction

Abstract The dark current transport mechanism in electrochemically deposited n-CdS/p-CdTe thin film heterojunctions is investigated. The forward current measured in the temperature range between 200° and 305°K can be expressed as Jf = J0(T) exp (AV) and the reverse current can be expressed as J r = −CV exp −CV[−λ(V d −V) −( 1 2 ) ] . The current mechanisms are consistent with a multi step recombination-tunneling model.

Optical properties of electrochemically deposited CdTe films

The optical properties of electrochemically deposited CdTe films were investigated. The index of refraction and the absorption coefficients in the 450–850‐nm range were measured for as‐deposited n‐type films and converted p‐type films. It was found that the converted p‐type films had higher optical absorption coefficients near the band edge than that of the n type. This change can be attributed to defect absorption. The absorption data yielded information concerning the band structure of the electrodeposited CdTe.

Hole traps in p‐type electrochemically deposited CdTe thin films

Deep level transient spectroscopy and photoluminescence measurements were performed for the first time on electrodeposited n‐CdS/p‐CdTe thin film solar cells. The observed levels were hole traps located at 0.2, 0.35, and 0.54 eV above the valence band. The nature of these hole traps can be attributed to the generation of Cd vacancies during the heat treatment step, which was used in device fabrication, to convert the as‐deposited n‐type films into p‐type layers.

The electronic characteristics of n‐type CdIn2Te4

The elecstronic properties of n‐type CdIn2Te4 crystals were investigated. The mobility and carrier concentration were measured using Hall techniques. I‐V and C‐V measurements were performed on Al/n‐CdIn2Te4 Schottky barrier devices. The I‐V data are interpreted in terms of space‐charge‐limited currents. The dominant electron trap level has been determined to be 0.21 eV below the conduction band. The barrier height was found to be approximately 0.65 eV.

Space-charge-limited current measurement of traps in p-type electrochemically deposited CdTe thin films

Abstract Space-charge-limited current measurements were performed on high resistivity p-type electrodeposited CdTe thin films. The observed dominant trap is a hole trap located at 0.54 eV above the valence band with a density of 1 × 10 14 cm −3

High-power, high-duty-cycle operation of monolithic two-dimensional surface-emitting diode laser arrays in the junction-down configuration

High-power, high-duty cycle and continuous wave operation of large-area monolithic 2D surface-emitting GaAlAs laser diode arrays mounted junction-down on microchannel heat exchangers have been demonstrated. Devices mounted don 2-mm-thick Cu heat spreaders were operated to peak output power densities of > 100 W/cm2 at 35% duty cycles,a nd exhibited high power conversion efficiencies, and full width emission spectra of < 4nm. Arrays mounted on 1-mm-thick heat spreaders were operated under continuous wave operating condition to approximately equals 50 W/cm2 power density levels. Silicon microchannel heat exchangers with a measured thermal resistance per unit are of 0.0324 degree(s)C cm2/W were used to removed up to 550 W/cm2 of excess heat generated by the arrays.

Index guided single stripe lasers fabricated by selective area growth in a metalorganic chemical vapor deposition system

Index guided single stripe lasers have been fabricated by using a one‐step selective area growth technique in the metalorganic chemical vapor deposition system. By pyrolytically depositing SiO or SiO2 layers on GaAs substrate, and lithographically defining the stripes, single stripe heterostructure lasers can be achieved on the uncovered substrate while polycrystalline films are observed beyond the stripe regions. The device operated with a single spatial mode for up to more than three times the threshold current.

High‐power broad‐area lasers fabricated by selective area growth

High‐power broad‐area stripe lasers have been fabricated by using a one‐step selective area growth technique in the metalorganic chemical vapor deposition system. This technique provides devices with excellent control both on electrical and optical confinements. cw output power of more than 350 mW/facet (700 mW total) was achieved, and a differential quantum efficiency of 0.625 mW/mA/facet (1.25 mW/mA total) was observed.