Yan-Ting Sun

Thermal strain in indium phosphide on silicon obtained by epitaxial lateral overgrowth

High-resolution x-ray diffraction reciprocal lattice mapping and low-temperature photoluminescence (PL) were used to study the thermal strain in InP layers grown on Si (001) substrate by hydride vapor-phase epitaxial lateral overgrowth (ELO) technique. Good agreement is found between the PL and x-ray measurements. We show that strain in the grown ELO InP/Si layers is affected by the aspect ratio (width to height ratio) of the ELO InP layer. Almost strain-free InP layer with high crystallographic quality is obtained on Si substrate, which is similar to that of a homoepitaxial InP layer.

Semi-insulating epitaxial layers for optoelectronic devices

Semi-insulating epitaxial layers of InP:Fe, GaAs:Fe and GaInP:Fe have been grown. To avoid the often observed inter-diffusion between Fe and Zn, two remedies are proposed using InP:Fe/InP:Zn as an example. One is co-doping InP with sulphur and iron and the other is to use ruthenium instead of iron. In situ mesa etching can also hinder side wall stimulated diffusion. Epitaxial lateral overgrowth studies of InP on a masked surface indicate promising feasibility of integrating SI InP on silicon. InP:Fe and GaInP:Fe/GaAs are found to be useful in the buried heterostructure laser fabrication. Buried in-plane lasers have shown very good thermal and high modulation properties. Buried vertical cavity surface emitting lasers can be pumped up to 97/spl deg/C under continuous operation.

Sulfur doped indium phosphide on silicon substrate grown by epitaxial lateral overgrowth

The epitaxial lateral overgrowth (ELOG) of sulfur doped InP from ring shaped openings on SiN/sub x/ masked InP/Si substrate in low pressure hydride vapor phase epitaxy system was investigated. Octahedral shaped ELOG InP templates with smooth surface were formed and studied by cathodoluminescence (CL). High energy transition at 825 nm (1.52 eV) due to the band filling effect caused by high concentration sulfur atoms trapped in threading dislocations was observed in spectra at 80 K. The band edge transition at 875 nm (1.42 eV) in CL spectra has no red shift caused by thermal strain. As observed in panchromatic image, defect free area was surrounded by high density threading dislocations that were pined by sulfur atoms due to impurity hardening. The quality of the ELOG InP templates is promising for the integration of photonic active layer on Si substrate.

Temporally resolved selective area growth of InP in the openings off-oriented from 110 direction

Temporally resolved selective area growth of InP on patterned substrates with openings off-oriented from [110] direction was studied by low pressure hydride vapour phase epitaxy system. Lateral ove ...

Study of planar defect filtering in InP grown on Si by epitaxial lateral overgrowth

InP thin films have been grown on InP/Si substrate by epitaxial lateral overgrowth (ELOG). The nature, origin and filtering of extended defects in ELOG layers grown from single and double openings in SiO2 mask have been investigated. Whereas ELOG layers grown from double openings occasionally exhibit threading dislocations (TDs) at certain points of coalescence, TDs are completely absent in ELOG from single openings. Furthermore, stacking faults (SFs) observed in ELOG layers grown from both opening types originate not from coalescence, but possibly from formation during early stages of ELOG or simply propagate from the seed layer through the mask openings. A model describing their propagation is devised and applied to the existent conditions, showing that SFs can effectively be filtered under certain conditions. ELOG layers grown from identical patterns on InP substrate contained no defects, indicating that the defect-forming mechanism is in any case not inherent to ELOG itself.

Temporally resolved growth of InP in the openings off-oriented from [110] direction

Temporally resolved growth of InP on patterned substrates with opening off-oriented from [110] direction was studied by low pressure hydride vapour phase epitaxy system. Lateral overgrowth and vertical growth were analysed. The lateral growth rate was observed to be strongly dependent on the orientation of the openings. The maximum lateral growth rate was achieved at 30/spl deg/ and 60/spl deg/ off [110] direction. The vertical growth rate was relatively constant, independent of the opening orientation. The optimum lateral overgrowth condition of InP was explored, which may be used for heteroepitaxy of InP on Si.

Selective growth of InP on focused-ion-beam-modified GaAs surface by hydride vapor phase epitaxy

The growth of InP islands on a planar focused-ion-beam (FIB)-modified (001) GaAs substrate was investigated in a hydride vapor phase epitaxy system. InP grew selectively on the FIB-implanted lines, forming continuous stripes, whereas isolated islands were observed outside the implanted area. The impact of the III/V ratio, crystallographic orientation of implanted lines, and implantation dose was explored. The choice of suitable growth conditions makes it possible to obtain continuous InP wires aligned in all possible directions. The results of this work could be used for the fabrication of future optoelectronic integrated circuits, which would include nanoscale structures, e.g., quantum-wire optical devices with GaAs electronic circuits.

Growth of InP directly on Si by corrugated epitaxial lateral overgrowth

In an attempt to achieve an InP-Si heterointerface, a new and generic method, the corrugated epitaxial lateral overgrowth (CELOG) technique in a hydride vapor phase epitaxy reactor, was studied. An ...

Demonstration of a quick process to achieve buried heterostructure quantum cascade laser leading to high power and wall plug efficiency

This thesis addresses new methods in the growth of indium phosphide on silicon for enabling silicon photonics and nano photonics as well as efficient and cost-effective solar cells. It also addresses the renewal of regrowth of semi-insulating indium phosphide for realizing buried heterostructure quantum cascade lasers with high power and wall plug efficiency for sensing applications.As regards indium phosphide on silicon, both crystalline and polycrystalline growth methods are investigated. The crystalline growth methods are: (i) epitaxial lateral overgrowth to realize large area InP on Si, for silicon photonics (ii) a modified epitaxial lateral overgrowth method, called corrugated epitaxial lateral overgrowth, to obtain indium phosphide/silicon heterointerface for efficient and cost effective solar cells and (iii) selective growth of nanopyramidal frusta on silicon for nanophotonics. The polycrystalline growth method on silicon for low cost solar cell fabrication has been realized via (i) phosphidisation of indium oxide coating synthesized from solution chemistry and (ii) phosphidisation cum growth on indium metal on silicon. All our studies involve growth, growth analysis and characterization of all the above crystalline and polycrystalline layers and structures.After taking into account the identified defect filtering mechanisms, we have implemented means of obtaining good optical quality crystalline layers and structures in our epitaxial growth methods. We have also identified feasible causes for the persistence of certain defects such as stacking faults. The novel methods of realizing indium phosphide/silicon heterointerface and nanopyramidal frusta of indium phosphide on silicon are particularly attractive for several applications other than the ones mentioned here.Both the polycrystalline indium phosphide growth methods result in good optical quality material on silicon. The indium assisted phosphidisation cum growth method normally results in larger grain size indium phosphide than the one involving phosphidisation of indium oxide. These two methods are generic and can be optimized for low cost solar cells of InP on any flexible substrate.The method of regrowth of semi-insulating indium phosphide that is routinely practiced in the fabrication of buried heterostructure telecom laser has been implemented for quantum cascade lasers. The etched ridges of the latter can be 6-15 µm deep, which is more than 2-3 times as those of the former. Although this is a difficult task, through our quick and flexible regrowth method we have demonstrated buried heterostructure quantum cascade lasers with an output power up to 2. 5 W and wall plug efficiency up to 9% under continuous operation.

An InP/Si heterojunction photodiode fabricated by self-aligned corrugated epitaxial lateral overgrowth

An n-InP/p-Si heterojunction photodiode fabricated by corrugated epitaxial lateral overgrowth (CELOG) method is presented. N-InP/p-Si heterojunction has been achieved from a suitable pattern containing circular shaped openings in a triangular lattice on the InP seed layer on p-Si substrate and subsequent CELOG of completely coalesced n-InP. To avoid current path through the seed layer in the final photodiode, semi-insulating InP:Fe was grown with adequate thickness prior to n-InP growth in a low pressure hydride vapor phase epitaxy reactor. The n-InP/p-Si heterointerface was analyzed by scanning electron microscopy and Raman spectroscopy. Room temperature cross-sectional photoluminescence (PL) mapping illustrates the defect reduction effect in InP grown on Si by CELOG method. The InP PL intensity measured above the InP/Si heterojunction is comparable to that of InP grown on a native planar substrate indicating low interface defect density of CELOG InP despite of 8% lattice mismatch with Si. The processed ...