R. F. Karlicek

Development of laser diagnostic probes for chemical vapor deposition of InP/InGaAsP epitaxial layers

Laser spectroscopic methods have been developed for the detection of PH3, P2, AsH3, As2, InCl, and GaCl, using both tunable‐dye‐laser induced fluorescence and excimer laser excitation. These are the primary reactants participating in the chemical vapor deposition (CVD) of InP/InGaAsP epitaxial layers. Using a reaction tube designed to simulate a CVD growth reactor, the detection limits measured for all these species are well below those levels typically employed during layer growth. Specific applications are outlined, and several examples are given relating these techniques to conditions expected in InP/InGaAsP layer growth.

Laser‐induced metal deposition on InP

It has been demonstrated that platinum can be deposited on p‐type, n‐type, and undoped InP via pulsed laser irradiation of polished substrates immersed in an aqueous solution of chloroplatinic acid. Pulsed laser intensities sufficient to initiate thermal decomposition of the InP surface, yet below the threshold at which gross surface damage occurs, cause elemental platinum to be deposited on the surface. The platinum deposits in the form of rectangular islands on the (100) surface and trigonal structures on the (111) InP surface. Under certain conditions, the islands grow together to form smooth platinum films ∼0.5 μm thick. Failure to form deposits at low laser powers indicates that platinum deposition occurs via a thermal mechanism. Auger electron analysis indicates that the platinum deposits are free of oxygen and chlorine contamination. Preliminary results also indicate that this technique may be used to deposit platinum on GaAs, nickel on InP (using aqueous NiSO4 solutions), and gold on InP (using bo...

UV absorption spectroscopy for monitoring hydride vapor‐phase epitaxy of InGaAsP alloys

Ultraviolet (UV) absorption spectroscopy has been used to monitor the concentrations of gas‐phase reactants participating in the growth of InGaAsP alloys by hydride vapor‐phase epitaxy. Room‐temperature absorption spectra for PH3, AsH3, and HCl as well as high‐temperature (700°C) spectra of InCl, GaCl, PH3,P2, P4, As2, and As4 are presented. For the group V species, the UV absorption bands of the hydride, dimer, and tetramer exhibit considerable overlap, but can still be used to determine the approximate concentration of each species. GaCl and InCl exhibit extremely intense, sharp absorption bands at 248 and 267 nm, respectively. This technique has been used to study the effect of PH3 pyrolysis on InP growth, and to monitor In/Ga ratio for metal transport from an alloy source. This technique can be implemented on reactor systems without reactor design changes and without disturbing the thermal profile by using ‘‘light pipes’’ to probe concentrations of reactive species during growth.

Thermal decomposition of metalorganic compounds used in the MOCVD of InP

Ultraviolet (UV) absorption spectroscopy has been used to monitor the thermal decomposition of Me3In, Me3In · PMe3, and Me3In · PEt3 employed in the metalorganic chemical vapor deposition (MOCVD) of InP. Both PMe3 and PEt3 were stable to 400°C, the high temperature limit of the optical cell. The onset of Me3In pyrolysis was observed at ∼ 270°C, and the activation energy was found to be ∼ 50 kcal/mol. The reversible dissociation of Me3In · PMe3 into its component alkyls occurred below 100°C. Though a similar behavior is presumed for Me3In ·sPEt3, its low vapor pressure precluded a determination of the temperature at which dissociation was complete. For both adducts, spectral changes at ∼ 300°C consistent with pyrolysis of free Me3In were observed. Based on these observations, it is suggested that these adducts prevent the reaction of free Me3In with PH3 only near room temperature, and that the nonvolatile polymer formed by reaction of Me3In with PH3 might be avoided by gas mixing at slightly elevated temperatures. Based on the relative thermal stabilities measured, a reaction sequence occurring for the deposition of InP is presented.

Channelled‐substrate buried heterostructure InGaAsP/InP lasers with vapor phase epitaxial base structure and liquid phase epitaxial regrowth

Channelled‐substrate buried heterostructure InGaAsP/InP lasers have been fabricated with vapor phase epitaxial grown base structures and liquid phase epitaxial regrowth. These devices have low pulsed threshold currents (14 mA minimum, median 19 mA), exhibit a pulsed threshold current temperature dependence with a characteristic temperature of 55 K, and operate cw up to 80 °C heat sink temperature. Life test results on these lasers have exhibited degradation rates in range 0–3 mA per thousand hours on burned‐in laser under 60 °C and 3 mW automatic power control accelerated aging conditions.

The Effect of PH[sub 3] Pyrolysis on the Morphology and Growth Rate of InP Grown by Hydride Vapor Phase Epitaxy

The incomplete pyrolysis of PH/sub 3/ is shown to have a significant effect on the growth rate and morphology of InP grown by hydride vapor phase epitaxy. Using ultraviolet absorption spectroscopy to determine the extent of PH/sub 3/ pyrolysis, the growth rate of InP is shown to increase with decreasing PH/sub 3/ pyrolysis. Incomplete PH/sub 3/ pyrolysis is also shown to dramatically increase the formation of growth hillocks on InP epitaxial layers. The use of various metal catalysts to expedite PH/sub 3/ pyrolysis to eliminate hillock formation during InP growth is described, and a qualitative model of PH/sub 3/ induced hillock growth is presented.

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...

A modified metalorganic chemical vapor deposition chemistry for improved selective area regrowth

Abstract Addition of HCl generated by pyrolysis of 1,1,1 trichloroethane (TCA) during both low pressure and atmospheric pressure MOCVD (metalorganic chemical vapor deposition) of InP has been used to improve the performance of the MOCVD selective area regrowth process. The addition of TCA provides good planar growth on unmasked areas without polycrystalline deposition on the mask or growth over the mask edges. Growth protrusions in the (111) direction for conventional MOCVD regrowth around re-entrant mesas are eliminated when TCA is added. TCA does not effect dopant incorporation or the ability to grow semi-insulating InP:Fe, but does cause a reduction in the growth rate proportional to the TCA partial pressure. Planarization of etched features without masks is also improved. Improved morphology is shown by demonstrating reproducible selective area InP regrowth around SiO2 capped etched mesas of various shapes, including reactive ion etched (RIE) mesas.

The growth of iron doped semi-insulating InP by hydride vapor phase epitaxy in a nitrogen ambient

Abstract The hydride vapor phase epitaxial (VPE) growth of semi-insulating (SI) InP: Fe using N2 as a carrier gas is reported. Iron doping was achieved by using FeCl2 generated in situ by reaction of HCl and powdered iron in a N2 carrier, and the transport of iron as FeCl2 was verified by optical absorption spectroscopy. In order to achieve InP growth in a N2 carrier input flowrates were adjusted to minimize the pyrolysis of PH3. The thermodynamics of FeCl2 transport and InP growth in an inert carrier are discussed, and preliminary results showing the growth of 108 Ω cm InP: Fe using this technique are presented.

TEM Observations of Laser‐Induced Pt and Au Deposition on InP

Les experiences de depots de Pt et Au a partir de solutions conduisent a la formation de Pt(P, In) 1 et de Au+Au 4 In