Junichiro Takeda

InGaAs nano-pillar array formation on partially masked InP(111)B by selective area metal–organic vapour phase epitaxial growth for two-dimensional photonic crystal application

We report on the selective area metal–organic vapour phase epitaxial growth of an InGaAs nano-pillar array on a partially masked InP(111)B substrate. This technique is very promising as a way to form semiconductor two-dimensional photonic crystals (2DPCs) suitable for infrared optical fibre communication. We successfully formed uniform hexagonal 2DPCs having vertical (110) facet sidewalls on 400 nm-pitch masked substrates. We observed vertical growth enhancement as well as the lateral overgrowth suppression for high aspect ratio InGaAs nano-pillar array formation under high growth-rate, long growth-time, and narrow window-opening conditions. We verified infrared emission from the InGaAs nano-pillar array by low-temperature photoluminescence measurement.

Size-dependent photoluminescence of hexagonal nanopillars with single InGaAs∕GaAs quantum wells fabricated by selective-area metal organic vapor phase epitaxy

The authors report the fabrication of the nanopillars with single InGaAs∕GaAs quantum well by selective-area metal organic vapor phase epitaxy. The standard diameter deviation of the nanopillars is about 8% and the standard deviation in their height about 5%. Their photoluminescence peak positions shift to the longer wavelength with an increase in the diameter of the nanopillars, which is not due to the quantum confinement effect in the radial or axial direction but due to the stoichiometry difference of the indium content in the nanopillars with different diameters.

Selective area MOVPE growth of two-dimensional photonic crystals having an air-hole array and its application to air-bridge-type structures

Abstract We describe a novel fabrication method of two-dimensional photonic crystals (2DPCs) by using selective area metal-organic vapor-phase epitaxial (SA-MOVPE) growth on (1 1 1) B masked substrates and its application to air-bridge-type structures with selective wet-chemical etching. This method is very promising as a way to form semiconductor 2DPCs because a PC membrane without process-induced damages can be obtained. To form uniform PC membranes having an air-hole array, we investigated the properties of SA-MOVPE regrowth on sub-micron-pitch masked substrates. We found that the optimum growth conditions strongly depend on the width of the GaAs opening as well as the pitch of the 2DPCs. An air-bridge structure having 250-nm-pitch 2DPC was also demonstrated by using a combination of SA-MOVPE regrowth and selective wet-chemical undercut etching.

Selective-area growth of hexagonal nanopillars with single InGaAs/GaAs quantum wells on GaAs(111)B substrate and their temperature-dependent photoluminescence

We report on the fabrication of highly uniform hexagonal nanopillars with single InGaAs/GaAs quantum wells (QW) on GaAs(111)B substrate by selective-area metal–organic vapour phase epitaxy. The standard size deviation of the fabricated nanopillars with single InGaAs/GaAs QW is about 2% and the standard deviation in their height about 5%. With a decrease in temperature, the peak position shifts to shorter wavelength, the peak intensity increases and the peak width decreases. The calculated well width based on the finite square potential well model taking account of the strain effect and the piezoelectric effect is smaller than the value determined from the growth rate and the growth time, which is mainly due to indium segregation and its incorporation into the subsequent GaAs layer grown at the higher temperature.

Promising low-damage fabrication method for the photonic crystals with hexagonal or triangular air holes: selective area metal organic vapor phase epitaxy

The photonic band diagrams of the photonic crystal slabs (PCSs) with various structural air holes were calculated by plane wave expansion method with super cell method. The calculated results indicate that the PCSs with hexagonal or triangular air holes have enough large photonic band gaps in the guided mode spectrum, hence they are good candidates to be used for the PC devices. The PCs with hexagonal or triangular air holes were fabricated successfully on n-type GaAs (111)B substrate by selective-area metal organic vapor phase epitaxy (SA-MOVPE). Vertical and smooth facets are formed and the uniformities are very good. The same process was also used to fabricate hexagonal air hole arrays with the width of 100 nm successfully. A procedure was proposed and utilized to fabricate the air-bridge PCS with normal hexagonal air holes. The fabricated hexagonal air holes are very uniform and the sidewalls are smooth and vertical. Our experimental results indicate that SA-MOVPE growth is a promising low-damage fabrication method for PC devices and photonic nano-strucutres.

Selective-area MOVPE fabrication of GaAs hexagonal air-hole arrays on GaAs(111)B substrates using flow-rate modulation mode

GaAs hexagonal air-hole arrays fabricated by selective-area metal-organic vapour phase epitaxy (SA-MOVPE) on patterned GaAs(111)B substrates are promising for applications to hexagonal air-hole-type two-dimensional photonic crystal (2D-PhC) slabs, because the grown structures exhibit smooth flat surfaces surrounded by crystal facets. In this paper, we describe SA-MOVPE carried out under various gas-flow sequences in order to reduce the growth temperature, and to obtain uniform air-hole arrays without lateral over-growth (LOG). We found that the growth rate in the pattern region and LOG were closely related to the effective As coverage and the desorption rate of the source materials. By optimizing SA-MOVPE, we obtained uniform hexagonal air-hole arrays with almost no LOG for arrays with 500?400?nm periodicity using alternate supply of the source materials (flow-rate modulation epitaxy mode). Finally, we successfully fabricated air-bridge-type hole arrays using selective etching of a sacrificial layer for vertical confinement of light in 2D-PhCs.

Growth of GaAs and InGaAs nanowires by utilizing selective area MOVPE

We report on the fabrication of GaAs and InGaAs hexagonal nanowires surrounded by {110} vertical facets on GaAs (111)B and InP (111)B substrates using selective area (SA) MOVPE growth. The substrate for SA-growth was partially covered with thin SiO/sub 2/ and circular mask opening with diameter d/sup 0/ of 50/spl sim/200 nm was defined. After SA-MOVPE, GaAs or InGaAs nanowires with the typical diameter d ranging from 50 nm to 200 nm and height 2 /spl mu/m to 9 /spl mu/m was formed vertically on the substrates, depending on the growth conditions and the pattern geometry. Possible growth mechanism is also discussed.

Formation of InP and InGaAs Air-Hole Arrays on InP(111) Substrates by Selective-Area Metal-Organic Vapor Phase Epitaxy

We report on a promising approach for the formation of compound semiconductor two-dimensional photonic crystal slabs utilizing selective-area metal–organic vapor phase epitaxy (SA-MOVPE). The selective-area growth process for the submicron-sized air holes of InP-based semiconductors was investigated on InP(111)A and (111)B substrates with a periodic array of hexagonal SiO2 masks. By optimizing growth conditions, a highly uniform array of hexagonal air holes in InP and InGaAs with a 500 nm pitch was formed on (111)B substrates. We also fabricated air-hole arrays with InP/InGaAs/InP double heterostructures on InP(111)B, and confirmed photoluminescence from an InGaAs quantum well at low temperatures.

Selective-area Growth of the Hexagonal Nano-pillars with Single InGaAs/GaAs Quantum Well and Their Temperature-dependence Photoluminescence

Hexagonal nano-pillars with single InGaAs/GaAs quantum well (QW) were fabricated successfully on the GaAs