Wilbur Dexter Johnston

Electrical characterization of Fe‐doped semi‐insulating InP grown by metalorganic chemical vapor deposition

The bulk resistivity of Fe‐doped metalorganic chemical vapor deposited grown epitaxial InP was determined from current‐voltage and capacitance measurements made on Schottky‐diode‐like devices. The current‐voltage data exhibit both an ohmic and a space‐charge‐limited regime, and the capacitance was found to be independent of applied bias. The electrical thickness was obtained from the capacitance using a relationship appropriate for current injection. Data for two samples representing both thin (∼1 μm) and thick (∼9 μm) epitaxial layers are presented. The resistivities were 6.5×107 Ωu2009cm and 2.2×108 Ωu2009cm.

Defect mechanisms in degradation of 1.3-μm wavelength channeled-substrate buried heterostructure lasers

Channeled-substrate buried heterostructure (CSBH) lasers which were purged from populations undergoing high reliability qualification have been studied in detail. Gradual and rapid degradation mechanisms leading to accelerated aging failure modes have been analyzed by transmission electron microscopy, convergent beam electron diffraction, electroluminescence, energy dispersive x-ray analysis, and chemical etching. The gradual degradation mode of CSBH lasers is characterized by (1) a gradual increase in room-temperature threshold current; (2) a decrease in external quantum efficiency, typically a drop in peak value of dL/dI greater than 25%; (3) a drop in forward voltage at low current, indicating a change in junction characteristics; (4) a large peak inI(dV/dI) below threshold (at around 3 mA); and (5) an enhancement in the peak in I2(d2V/dI2) at laser threshold. A defect mechanism associated with the gradual degradation begins with a nucleation of extrinsic dislocation loops along the V-groove {111} p-n–...

Interfacial microstructure and electrical properties of the Pt/Ti ohmic contact in p-In0.53Ga0.47As formed by rapid thermal processing

The interfacial microstructure and electrical properties of the Pt/Ti ohmic contact to p‐In0.53Ga0.47As (Zn: 5×1018 cm−3) formed by rapid thermal processing (RTP) were intensively studied. Significant interdiffusion of Ti, In, and As across the interface, driven by RTP, occurred at temperatures of, or above, 350u2009°C for a heating duration of 30 s. A minimum specific contact resistance (9.0×10−6 Ωu2009cm2) was achieved after heating at 450u2009°C. Cross‐sectional transmission electron microscopy of this sample revealed an interfacial reaction zone with complicated microstructure, and the dominant interfacial compound was identified to be InAs. Further increase in RTP temperature resulted in a change in the microstructure, and degradation of the contact resistance. The temperature‐dependence characteristic of the specific contact resistance of as‐deposited Pt/Ti contact to InGaAs revealed a thermionic‐emission‐dominated carrier‐transport mechanism with an effective barrier height φb, of 0.13 V. RTP treatment to the ...

A transmission electron microscope study of iron phosphide precipitates in InP crystals

Abstract A transmission electron microscope was used to study the nature of small (100–250 A) precipitates observed in semi-insulating Fe-doped InP layers grown by metalorganic chemical vapor deposition technique on (001) InP substrates. Since these precipitate particles did not dissolve in a Br-methanol etching solution, it was possible to isolate the particles on a carbon-coated electron microscope grid. Both electron diffraction and X-ray energy dispersive techniques have shown unambiguously that these particles are stoichiometric FeP crystals.

A study of Fe-dopants for growth of semi-insulating InP by MOCVD

Abstract SIMS depth profiling has been used to measure the Fe concentrations in Fe-doped InP epitaxial layers, grown by MOCVD, using a variety of dopant sources. Iron-olefin carbonyl sources were found to give smoother and more uniform doping profiles than Fe(C5H5)2, although similar electrical properties were obtainedproviding the Fe concentration was below ∼8×1018 cm−3. For the majority of samples analyzed, resistivities ⩾ 4×107 Ω cm were measured. From the temperature dependence of the resistance of the material, an activation energy of 0.68 eV was calculated, in excellent agreement with the values previously obtained for bulk Fe-doped InP.

Defect structure in III-V compound semiconductors: generation and evolution of defect structures in InGaAs and InGaAsP epitaxial layer grown by hydride transport vapor-phase epitaxy

The generation and evolution of a novel defect structure in InGaAs single‐layer and InGaAsP/InP multilayer laser structures grown by hydride transport vapor‐phase epitaxy on (001)InP substrate has been studied in detail using both cross‐section and plan‐view transmission electron microscopy. Under certain growth conditions, a unique defect structure consisting of a dislocation tangle initiated at the InGaAs/InP interface, having the shape of a pyramid, followed by a bundle of straight dislocations propagating through the InGaAs epitaxial layer near [001] growth direction and along 〈112〉 orientations, is formed. Such defect structure is universal to these materials grown from vapor sources. The pyramidal‐dislocation tangles, or PDT defects, are formed as a result of the agglomeration of fine precipitates (500 A in size) which generate a special type of edge dislocation lying in the (110) plane with the line direction oriented close to the [001] growth direction. X‐ray microanalysis indicates that the inter...