We demonstrate a surface emitting 1.5 mu m multi-quantum well (MQW) light-emitting diode (LED) on a 3-inch epitaxial lateral overgrowth (ELOG) InP/Si wafer. The enhanced crystalline quality of ELOG InP/Si is revealed by various characterization techniques, which gives rise to a MQW with high photoluminescence intensity at 1.5 mu m and interference fringes arising from the vertical Fabry-Perot cavity. The LED devices exhibited strong electroluminescence intensity that increased with pump current. Moreover, transparency current measurements indicate optical gain in the 1.5 mu m MQW on InP/Si. The results are encouraging for obtaining wafer scale 1.5 mu m surface emitting laser structures on silicon with further optimization.

Buried heterostructure (BH) lasers are routinely fabricated for telecom applications. Development of quantum cascade lasers (QCL) for sensing applications has largely benefited from the technological achievements established for telecom lasers. However, new demands are to be met with when fabricating BH-QCLs. For example, hetero-cascade and multi-stack QCLs, with several different active regions stacked on top of each other, are used to obtain a broad composite gain or increased peak output power. Such structures have thick etch ridges which puts severe demand in carrying out regrowth of semi-insulating layer around very deeply etched (>10 mu m) ridges in short time to realize BH-QCL. For comparison, telecom laser ridges are normally only <5 mu m deep. We demonstrate here that hydride vapour phase epitaxy (HVPE) is capable of meeting this new demand adequately through the fabrication of BH-QCLs in less than 45 minutes for burying ridges etched down to 10-15 mu m deep. This has to be compared with the normally used regrowth time of several hours, e.g., in a metal organic vapour phase epitaxy (MOVPE) reactor. This includes also micro-stripe lasers resembling grating-like ridges for enhanced thermal dissipation in the lateral direction. In addition, we also demonstrate HVPE capability to realize buried heterostructure photonic crystal QCLs for the first time. These buried lasers offer flexibility in collecting light from the surface and relatively facile device characterization feasibility of QCLs in general; but the more important benefits of such lasers are enhanced light matter interaction leading to ultra-high cavity Q-factors, tight optical confinement, possibility to control the emitted mode pattern and beam shape and substantial reduction in laser threshold.

Optical and structural properties of sulfur-doped epitaxial lateral overgrowth (ELOG) InP grown from nano-sized openings on Si are studied by room-temperature cathodoluminescence and cross-sectional transmission electron microscopy (XTEM). The dependence of luminescence intensity on opening orientation and dimension is reported. Impurity enhanced luminescence can be affected by the facet planes bounding the ELOG layer. Dark line defects formed along the [011] direction are identified as the facet planes intersected by the stacking faults in the ELOG layer. XTEM imaging in different diffraction conditions reveals that stacking faults in the seed InP layer can circumvent the SiO<inf>2</inf> mask during ELOG and extend to the laterally grown layer over the mask. A model for Suzuki effect enhanced stacking fault propagation over the mask in sulfur-doped ELOG InP is constructed and in-situ thermal annealing process is proposed to eliminate the seeding stacking faults.

III-V semiconductors are suitable for high efficiency and radiation resistant solar cells. However, the high cost of these materials limited the application of these solar cells only for specialty application. High quality polycrystalline III-V thin films on low cost substrate are the viable solutions for the problem. In this work we demonstrate two new approaches to grow polycrystalline InP on Si(001) substrate. (i) A simple chemical solution route which makes use of deposition of In2O3 on Si and its subsequent phosphidisation and (ii) In assisted growth that involves deposition of In metal on Si and subsequent growth of InP from its precursors in hydride vapor phase epitaxy. Both techniques are generic and can be applied to other semiconductors on low cost and flexible substrates.

Epitaxial lateral overgrowth of InP has been grown by hydride vapor phase epitaxy on Si substrates with a thin seed layer of InP masked with SiO2. Openings in the form of multiple parallel lines as well as mesh patterns from which growth occurred were etched in the SiO2 mask and the effect of different growth conditions in terms of V/III ratio and growth temperature on defects such as threading dislocations and stacking faults in the grown layers was investigated. The samples were characterized by cathodoluminescence and by transmission electron microscopy. The results show that the cause for threading dislocations present in the overgrown layers is the formation of new dislocations, attributed to coalescence of merging growth fronts, possibly accompanied by the propagation of pre-existing dislocations through the mask openings. Stacking faults were also pre-existing in the seed layer and propagated to some extent, but the most important reason for stacking faults in the overgrown layers was concluded to be formation of new faults early during growth. The formation mechanism could not be unambiguously determined, but of several mechanisms considered, incorrect deposition due to distorted bonds along overgrowth island edges was found to be in best agreement with observations.

Together with the optimal basic design, buried heterostructure quantum cascade laser (BH-QCL) with semi-insulating regrowth offers unique possibility to achieve an effective thermal dissipation and lateral single mode. We demonstrate here for the first time realization of BH-QCLs with a single step regrowth of highly resistive (>1x10(8) ohm.cm) semi-insulating InP:Fe in less than 45 minutes in a flexible hydride vapour phase epitaxy process for burying ridges etched down to 10-15 mu m deep both with and without mask overhang. The fabricated BH-QCLs emitting at similar to 4.7 mu m and similar to 5.5 mu m were characterized. 2 mm long 5.5 mu m lasers with ridge width 17-22 mu m, regrown with mask overhang, exhibited no leakage current. Large width and high doping in the structure did not permit high current density for CW operation. 5 mm long 4.7 mu m BH-QCLs of ridge widths varying from 6-14 mu m regrown without mask overhang, besides being spatially monomode, TM00, exhibited WPE of similar to 8-9% with an output power of 1.5 - 2.5 W at room temperature and under CW operation. Thus, we demonstrate a simple, flexible, quick, stable and single-step regrowth process with extremely good planarization for realizing buried QCLs leading to monomode, high power and high WPE.

Together with the optimal basic design, buried heterostructure quantum cascade laser (BH-QCL) with semi-insulating regrowth offers a unique possibility to achieve an effective thermal dissipation and lateral single mode. We demonstrate here the realization of BH-QCLs with a single-step regrowth of highly resistive (>1 x 10(8) ohm . cm) semi-insulating InP: Fe in <45 min for the first time in a flexible hydride vapor phase epitaxy process for burying ridges etched down to 10 to 15 mu m depth, both with and without mask overhang. The fabricated BH-QCLs emitting at similar to 4.7 and similar to 5.5 mu m were characterized. 2-mm-long 5.5-mu m lasers with a ridge width of 17 to 22 mu m, regrown with mask overhang, exhibited no leakage current. Large width and high doping in the structure did not permit high current density for continuous wave (CW) operation. 5-mm-long 4.7-mu m BH-QCLs of ridge widths varying from 6 to 14 mu m regrown without mu mask overhang, besides being spatially monomode, TM00, exhibited wall plug efficiency (WPE) of similar to 8 to 9% with an output power of 1.5 to 2.5 W at room temperature and under CW operation. Thus, we demonstrate a quick, flexible, and single-step regrowth process with good planarization for realizing buried QCLs leading to monomode, high power, and high WPE.

Nanosized octagonal pyramidal frusta of indium phosphide were selectively grown at circular hole openings on a silicon dioxide mask deposited on indium phosphide and indium phosphide pre-coated silicon substrates. The eight facets of the frusta were determined to be {111} and {110} truncated by a top (100) facet. The size of the top flat surface can be controlled by the diameter of the openings in the mask and the separation between them. The limited height of the frusta is attributed to kinetically controlled selective growth on the (100) top surface. Independent analyses with photoluminescence, cathodoluminescence and scanning spreading resistance measurements confirm certain doping enrichment in the frustum facets. This is understood to be due to crystallographic orientation dependent dopant incorporation. The blue shift from the respective spectra is the result of this enrichment exhibiting the Burstein-Moss effect. Very bright panchromatic cathodoluminescence images indicate that the top surfaces of the frusta are free from dislocations. The good optical and morphological quality of the nanopyramidal frusta indicates that the fabrication method is very attractive for the growth of site-, shape-, and number-controlled semiconductor quantum dot structures on silicon for nanophotonic applications.

A simple method of growing large areas of InP on Si through Epitaxial Lateral Overgrowth (ELOG) is presented. Isolated areas of high quality InP suitable for photonic integration are grown in deeply etched SiO2 mask fabricated using conventional optical lithography and reactive ion etching. This method is particularly attractive for monolithically integrating laser sources grown on InP with Si/SiO2 waveguide structure as the mask. The high optical quality of multi quantum well (MQW) layers grown on the ELOG layer is promisingly supportive of the feasibility of this method for mass production.

Monolithic integration of InP based structures on Si for optical interconnects is presented. Different strategies are demonstrated to achieve requisite InP platform on Si. In the first strategy, defect free isolated areas of epitaxially and laterally overgrown InP are obtained on Si and the InGaAsP based quantum wells directly grown on these templates have shown high material quality with uniform interfaces. In the second strategy, selective area growth is exploited to achieve InP nano pyramids on Si which can be used for the growth of quantum dot structures. In the third and the final strategy, a method is presented to achieve direct interface between InP and Si using corrugated epitaxial lateral overgrowth.