Tsukuba city was built to function as a science city about twenty years ago, and today integrates over 45 national research institutes, three universities, and more than 150 private research centers. Since the IPRM conference was first established in 1989, its steadily increasing importance has been demonstrated by the growing number of participants and the submission of numerous high quality papers spanning the gamut from basic research to manufacturing and production. The IPRM98 conference marks a milestone in our conference history commemorating the tenth anniversary of the IPRM series.
Over 400 participants distributed throughout Asia, Europe, Canada, the USA and Africa attended the meeting. In total 227 papers were presented in four and one half days. This included 22 invited, 3 plenary, 191 contributed papers and 11 post deadline talks. Papers were selected from 6 Areas; Opto-electronics (65), Electron devices (35), Processing (23), Epitaxy (33), Bulk & Characterization (33), and New Materials & Nanostructures (37). Following is a summary of these topics as well as a brief description of Short Courses and the Rump Session highlights.
The Short Course program was initiated on the Monday, May 11 prior to the regular sessions. The three topics covered were epitaxy, electron devices, and photonic devices. Well known experts conducted these s. The first minicourse was a lecture on OMCVD of InP-based heterostructures by Dr. Rajaram Bhat of Corning Inc. He spoke about fundamental issues as well as recent advances of InP metal-organic vapor phase epitaxy. Next in the sequence, Prof. April S. Brown, Georgia Institute of Technology talked about InP-based electronics: materials to applications. She emphasized molecular beam epitaxy of InP materials and focussed on how fundamental electronic properties are effected by growth conditions. The final lecture by Dr. Yuichi Tohmori of NTT Optoelectronics Labs addressed InP-based photonic devices for telecommunications. WDM devices for optical cross connect and access network applications were mainly discussed. Over 80 delegates attended this pre-conference event which featured interesting lectures followed by lively interactive discussion.
Optoelectronics In the Plenary and 10th Anniversary Invited talks, Arakawa (Univ. Tokyo), Erman (Alcatel) and Kobayashi (NEC) reviewed the technical development of future optical networks, focussing on the key issues of high speed, DWDM and low cost. Lorl (HHI) reported a 40 GHz Mach-Zehnder Optical Demultiplexer which featured a traveling wave electrode and a tunneling barrier QW structure. In DWDM, Arrayed Waveguide Grating (AWG)-integrated lasers and photo-detectors with a wavelength-spacing of 50 GHz were demonstrated by NTT. The long term wavelength stability of cooled DFB LDs was tested at Lucent. Low cost, packaged, LDs and high-temperature operation with low power consumption were also reported. Sato (Hitachi) showed that the driving current of a 1.3 mm beam expander (BEX) or spot size converter (SSC) integrated LD was dramatically reduced by using n-type modulation doped MQW active layers. Takemasa (Oki) demonstrated the effectiveness of the p-type AlInAs electron stopper layer in the 1.3 mm AlGaInAs/InP strained MQW LDs for high temperature operation and obtained CW operation at 150 oC (To>120K).
Electron Devices Next generation InP-based HBT technology has been developed by TRW. These devices are based on their GaAs HBT process which produces advanced HBT integrated circuits for high volume commercial applications. Advanced transferred-substrate HBT technology has been reported from UCSB. For example, this new technology yields high performance static frequency dividers with peak operation at 48 GHz. In HFET research, InP-based MMICs with lower noise and higher gain has been developed for applications in communication and sensor systems operating at millimeter-wave frequencies. Practical use of resonant tunneling devices has been also reported by several groups for digital circuit applications. Recent progress on the integration of RTD/HEMT, RTD/HBT, RTD/PD etc. was also presented in this conference.
Processing Several techniques for surface passivation of InP were reported. Takahashi et al (Hokkaido Univ) have realized a low interface state density of Nss=2x1010 by the nitridation of thin Si layers grown on InP by MBE followed by deposition of Si3N4 films. Lorenzo et al (Air Force Res. Lab.) have succeeded in unpinning the InP surface by combining MBE grown CdS layers (thickness: 5-6 nm) and deposited SiO2 films. MIS diodes result in minimal frequency dispersion and the quasi-static C-V is near ideal. Fabricated MISFETs are stable with over 100ms/mm for a 1.5mm gate. Driad et al (Nat. Res. Council, Canada) has reported reduced leakage base current HBTs by depositing SiO2 films after oxidation of InP surface under the ultra-violet excited ozone atmosphere and etching by HF. High reliability long wavelength BH lasers were fabricated by the combination of ECR-RIBE etching with Cl2 gases and wet chemical etching (Matsushita Electronics). ECR-RIBE etching (CNET) followed by low growth rate OMVPE re-growth results defect reduction and a corresponding increase of carrier lifetime for 1.55 mm gain coupled DFB lasers. The devices were fabricated using 70keV-Ga FIB scanning (Wurzburg Univ.). Reported device results are extemely promising.
Selective growth by MOVPE Epitaxy was widely used as a key technology for the fabrication of optoelectronic devices and their integration. Modulator integrated MQW-DFB LDs were fabricated by using narrow-stripe area selective MOVPE growth. Both thickness and indium content of the layers selectively grown between the dielectric mask stripes varies with the stripe width resulting in a change in the effective bandgap energy with the stripe width. For thier contribution to the development of this technology, three groups, NEC, Hitachi and University of Gent, received the IPRM 10th Anniversary Paper Award. This technology was also used to fabricate different wavelength MQW-LDs in a single growth run by combination with EB lithography. Ruthenium was demonstrated as a new thermally stable compensator in InP (Tech. Univ. Berlin). The diffusion coefficient was as low as 1x10cm2/s at 800oC and resistivities of 107-108 W.cm were obtained.
Bulk & Characterization Crystal growth of 100 mm and 75 mm diameter VGF d oriented InP and 100 mm diameter VCZ d oriented InP has been first reported. Vapor phase doping of Fe based on wafer annealing for preparing 75 mm diameter semi-insulating InP wafers was developed, allowing consistent Fe concentrations from wafer to wafer. Of particular interest is the fact that 4 substrate manufacturers displayed 100 mm diameter wafers during the exhibition.
New materials and nanostructures A 10 mm three-dimensional photonic band-gap structure was demonstrated in GaAlAs material system by a novel approach based on wafer-fusion technology. This paper received the best student (IEEE/LEOS) award of IPRM98. The quantum-dot (QD) structure addressed low-threshold (360 A/cm2) InAs/GaAs-QD laser diodes and the Coulomb-Blackade effect AlAs/InAs QD structures. The new material system GaInNAs was the topic of an open discussion on How we can improve crystal quality to achieve temperature-insensitive threshold current long-wavelength laser diodes and VCSELs; is it a result of the material property itself, or not?.
A Rump Session entitled Myths and Realities of InP Materials and Devices was held on May 13, presided by K. Oe (KIT) and R. Bhat (Corning). The session was introduced by an interesting market survey/review of substrates and epitaxial wafers. The survey concluded that, given the high yield claims of device houses, a large percentage of InP wafers must be consumed in research activities. Markets of semiconductor lasers and detectors are shown to increase every year by over 10 %. Wafer and electronic device discussions highlighted the performance aspects of InP technologies, concluding that (electronic) InP devices will find their best niche in high frequency applications. Cost however is still a major driver/barrier.
The IPRM99 conference will be held in Davos, Switzerland, 16-20 May, 1999.
T: +41 1 633 21 01,
F: +41 1 633 11 09,
Paper submission Deadline 05 December 1998.
IPRM99 Web site: http://www.iqe.ethz.ch/iprm99
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