Sung June Kim

Area selectivity of InGaAsP-InP multiquantum-well intermixing by impurity-free vacancy diffusion

Area selectivity of bandgap tuning in the InGaAsP-InP multiquantum-well structure has been investigated using low temperature photoluminescence (PL). The bandgap blue-shift in the intermixed region was as much as 170 meV for a rapid thermal anneal of 30 s at 850/spl deg/C, and was controllable using annealing temperature and time. From samples with SiO/sub 2/ stripe patterns, clearly separated PL peaks were observed centered at 0.95 and 1.08 eV, each representing signals originating from the dielectric capped and exposed areas, respectively. In samples with stripes intervals less than 6 /spl mu/m, PL signals did not separate, but formed one broad spectrum due to lateral diffusion. The lateral diffusion was found less than 3.0 /spl mu/m.

Low temperature photoluminescence characteristics of Zn-doped InP grown by metalorganic chemical vapor deposition

Zn-doped InP layers were obtained by two different doping techniques: in situ doping by low pressure metalorganic chemical vapor deposition, and thermal diffusion from a Zn-containing film. Their low temperature photoluminescence (PL) characteristics were studied, and compared. In Zn-diffused InP, the deep donor to acceptor transition was the most dominant transition and other transitions such as the band edge transition and the band to band or shallow donor to acceptor transition were not observed at the excitation power of 10 mW. On the other hand, well resolved band edge peaks and the band or shallow donor to acceptor transition peak were observed for in situ Zn doped InP, implying that less interstitial Zn atoms were generated during in situ doping. Saturation of the hole concentration at 1.5×1018 cm3 was observed in in situ Zn doped InP, and the changes in PL characteristics at the saturation level were extensively studied. Two new deep bands at 0.88–1.0 eV and 1.21–1.27 eV were observed, and the int...

Characteristics of intermixed InGaAs/InGaAsP Multi-Quantum-Well Structure

The intermixing of a InGaAs/InGaAsP multi-quantum-well (MQW) structure induced by SiO2 dielectric cap layer deposition and heat treatment was investigated. Photoluminescence experiments reveal a large blue shift of the effective bandgap for the intermixed quantum well. By secondary ion mass spectroscopy, the group III and V elements of a MQW are found to interdiffuse at a similar rate after the intermixing process. An optical waveguide was fabricated using intermixed material where a propagation loss reduction of 450 dB was recorded at a wavelength close to the original bandgap wavelength.

Integration of waveguide-type wavelength demultiplexing photodetectors by the selective intermixing of an InGaAs-InGaAsP quantum-well structure

Using the selective intermixing of an InGaAs-InGaAsP multiquantum-well (MQW) structure, a wavelength demultiplexing photodetector which can demultiplex two widely separated wavelengths was fabricated. An InGaAs-InGaAsP MQW with a u-InP cladding layer and a n-InGaAs cap layer, grown by metal organic chemical vapor deposition was used. Selective area intermixing of the InGaAs-InGaAsP MQW structure was done by a rapid thermal annealing after the deposition and patterning of the SiO/sub 2/ dielectric layer on the InGaAs cap layer. The integrated structure consists of shorter and longer wavelength sections, separated by an absorber section. Shorter wavelength and absorber sections were intermixed with the SiO/sub 2/ dielectric layer. At a wavelength of 1477 nm, the output photocurrent ratio was enhanced as the length of the absorber region increased and a ratio of over 30 dB was observed, while at a wavelength of 1561 nm, an output photocurrent ratio of 18.9 dB was observed.

INTERMIXING CHARACTERISTICS OF STRAINED-INGAAS/INGAASP MULTIPLE QUANTUM WELL STRUCTURE USING IMPURITY-FREE VACANCY DIFFUSION

The quantum well intermixing of a strained InGaAs/InGaAsP multiple quantum well using an impurity-free vacancy diffusion technique has been studied. The bandgap wavelength of quantum well was changed by the intermixing from 1.55 µm band to 1.3 µm band with a wavelength shift of 237 nm. The transformation from a multiple quantum well structure to a homogeneous alloy was observed. The strain-enhanced intermixing rate and self-interdiffusion rate were observed.

Integration of waveguide type wavelength demultiplexing photodetectors by selective intermixing of InGaAs/InGaAsP quantum well structure

Wavelength demultiplexing photodetectors was fabricated using selective intermixing of InGaAs/InGaAsP multi-quantum well (MQW) structure. As InGaAs/InGaAsP MQW with U-InP cladding layer and U-InGaAs cap layer grown by metal organic chemical vapor deposition (MOCVD) was used for this experiment. Intermixing of InGaAs/InGaAsP MQW structure was done by a rapid thermal annealing after depositing SiO2 dielectric layer on the InGaAs cap layer by plasma-enhanced chemical vapor deposition (PECVD). Three sections of shorter-wavelength PD, absorber region and longer-wavelength PD lined up linearly and the front two regions were intermixed. Output current ratios of fabricated photodetectors at wavelengths of 1550 and 1480 nm were about 20dB and thus the photodetectors were proven to demultiplex both wavelengths.

Deep levels in heavily Zn-doped InP layers implanted with Ti and Ti/P

We have investigated deep level peaks observed in the photoluminescence spectrum of heavily Zn-doped InP layers grown by metalorganic chemical vapor deposition at energies centered at 0.89 and 0.94 eV. These peaks are enhanced when the samples are implanted with Ti. When P is co-implanted, however, the intensity of these peaks decrease, and at an increased dosage, the peaks disappear from the spectrum. The peaks are, therefore, dependent on the phosphorus vacancy produced by the excessive Zn doping or the implant damage. Hall measurement data show that the Ti/P-implanted p-type InP layer is converted to n type with its sheet resistance decreasing and the donor activation of Ti increasing for higher P co-implant dose. In addition, the photoluminescence intensity of the deep level peaks is highly correlated with the sheet resistance.

Large bandgap shift in InGaAs(P)/InP multi-quantum well structure obtained by impurity-free vacancy diffusion using SiO2 capping and its application to photodetectors

In this paper, we have investigated the bandgap tuning in the InGaAs InP multiquantum well structure obtained by impurity-free vacancy diffusion using low temperature photoluminescence (PL). The MQW intermixing was performed in a rapid thermal annealer (RTA) using the dielectric capping materials, SiO2 and SiNx. The SiO2 capping was successfully used with InGaAs cap layer to cause a large bandgap tuning effect in the InGaAs/InP MQW material. The blue shift of bandgap energy after RTA treatment was as much as 185 and 230 meV at 750 degrees C and 850 degrees C, respectively, with its value controllable using annealing time and temperature. Samples with SiO2-InP or SiNx- InGaAs cap layer combinations, on the other hand, did not show any significant energy shifts. The absorption spectra taken from the same samples confirmed the energy shifts obtained using PL. The process development can be readily applied to fabrication of photodetectors that are sensitive to wavelength and/or polarization.

Photoluminescence characteristics of Cd and Zn diffused layers in InP

Cd and Zn diffused InP have been characterized using low temperature PL (photoluminescence). The diffusion was done at three temperatures using evaporated diffusion source in a rapid thermal annealer (RTA). Band to acceptor (B-A) transition dominates in the PL spectra of InP:Cd, whereas InP:Zn shows donor to acceptor (D-A) transitions with blue-shift tendency for higher excitation power. This indicates the presence of much higher concentration of interstitials acting as donors in InP:Zn than in InP:Cd. Furthermore the D-A peak in InP:Zn moves to lower energy (red-shift) for higher diffusion temperature, which is attributed to the increase in number of nonradiative recombination centers.