FEATURE OPTOELECTRONICS
InP epitaxial crystals support 5g applications
Words by Dr. Gako Araki, Marktech Optoelectronics, & Molly Bakewell Chamberlin, Embassy Global
A hand-drawn diagram of an InP wafer’s
typical structure
of lnP epitaxial crystal manufacturing, using mass-production MOCVD equipment known as GAKOUS. Given that true lnP-HBT epitaxial crystal performance testing requires electrical characteristic evaluations on larger HBT devices, Marktech instead focused R&D efforts on new manufacturing equipment which could produce InP-HBT epitaxial crystals with the necessary uniformity, quality and size for ultra-high-speed signal processing. These goals were successfully achieved via a new crystal manufacturing method: carbon-doped InGaAs growth, without hydrogen.
I
n a recent study released by mobile communications industry researchers, GSMA, 5G networks are projected to account for 15 per cent of all global mobile connectivity by 2025. Network performance goals appear to centre around improved device connectivity, higher-speed data rates, reduced latency, energy and cost savings and expanded system capacities. These needs can be attributed, in part,
to equally sharp, observable increases in internet end-user traffic volumes and mobile device usage. Those needs have led to an emerging demand for communication systems that are capable of ultra-high-speed, large-capacity signal processing. In the case of wired systems, advancements in time division and wavelength division multiplexing systems has enhanced their signal- handling capacities. With this demand for effective signal processing, one requires a qualified, proficient component to deliver. GaAs and SiGe semiconductor components are typically specified for commercial transfer speeds of up to 10Gbits/s. But many believe that the performance ceilings of these materials will limit maximum transfer rates to 40Gbits/s. However, for ultra-high-speed circuits exceeding 40-Gbit/s, anticipation is high for devices whose designs incorporate faster lnP semiconductor components. This leads us onto a core factor.
28 JUNE 2019 | ELECTRONICS
THE SIGNIFICANCE OF INP EPITAXIAL CRYSTALS FOR 5G Since lnP semiconductors offer higher average carrier throughput than can be found with ordinary saturation velocity, they present significant application advantages for 5G. Among several types of lnP electronic devices, active R&D is currently underway to commercialise both heterojunction bipolar (HBT) and high-electron mobility transistors (HEMT).
Determinations of the basic performance characteristics of related transistor elements, such as lnP HBT and HEMT, are largely dependent on the material and structural properties of the chipset epitaxial layer. The creation of a stable supply of low-cost chipsets with uniform element characteristics and circuitry properties, requires elevated uniformity in both epitaxial layer composition and film thickness, combined with reduced impurity content rates. The successful development of mass-production technologies for achieving these goals is the topic of recent research undertaken by Marktech Optoelectronics.
MOCVD GAKOUS R&D was carried out in two distinct phases. Phase one consisted of 5G lnP epitaxial crystal growth technology development, using small prototype MOCVD equipment. Phase two consisted
Dr. Gako Araki, head of R&D for ultra-high speed applications, Marktech Optoelectronics
TESTING THE MOCVD TECHNOLOGY AND ITS INP EPITAXIAL CRYSTALS The Marktech evaluation of the small MOCVD prototype showed favorable performance characteristics. Marktech then performed successful, high- frequency HBT electrical characterisations on the prototype, with equally favorable results. As a result, Marktech was able to conclude its successful development of MOCVD GAKOUS, whose capabilities offer the necessary prototype growth technology for manufacturing quality control within 5G-related applications. As a final accompaniment to this R&D, Marktech developed a series of non-destructive, electron mobility measurement systems. This included time-resolved photoluminescence testing, with infrared wavelength area measurements. Using these techniques, it was determined that the Marktech MOCVD prototype exhibited satisfactory performance with new organic materials, independent source injection and a narrow gap placed between the injector and surface, to avoid surface reactions. Consequently, Marktech developed its new MOCVD GAKOUS equipment to produce lnP epitaxial crystals that could offer sufficient quality and uniformity for larger-scale commercial lnP HBT and HEMT crystal production volumes. Because of this successful R&D, Marktech is now offering this technology to the 5G industry, for their ultra-high- speed signal processing applications.
Marktech Optoelectronics
www.marktechopto.com
/ ELECTRONICS
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