Keysight Technologies, Inc. says it has successfully tested new chipsets that take advantage of the firm’s indium phosphide (InP) semiconductor technology. Keysight expects the new chipsets will help deliver real-time and equivalent-time oscilloscopes in 2017 that offer bandwidths exceeding 100 GHz with significantly better noise floors than what is currently on the market.
InP is a binary semiconductor having a face-centered cubic crystal structure like that of GaAs and most of the III-V semiconductors. The InP-based material system consists of InP and alloys of InGaAs and InAlAs lattice-matched to the InP substrate.
InP transistors have a thicker base and collector layers than in Si, SiGe, and GaAs devices. That gives them a loser current density for peak performance, (top) and a higher electron velocity for a higher voltage breakdown figure at high electric field strengths.
To make an InP semiconductor, a lattice-matched epitaxial film is grown with the right ratios of the elements to adjust the lattice parameter to equal that of the substrate. InGaAs lattice-matched to InP, for instance, has 53% InAs and 47% GaAs.
InP has an electron effective mass me* = 0.075 m0, and its conduction band structure allows a higher electron velocity at much higher fields compared to GaAs or InGaAs. InP devices typically have an extremely low noise figure
and are useful through W-band and beyond. Typically, InP semiconductors use various combinations of InGaAs, InAlAs, and InP layers through the device structure which is one of the reasons such semiconductors have a complex makeup.
InP-based bipolar transistors typically have heterojunctions inside the device structure, with different semiconductor materials used on each side of the base-emitter and base-collector junctions.This complicates the manufacture of these devices but also facilitates device performance that could not be realized otherwise.
Keysight says the real-time oscilloscopes using the InP devices will also feature a new 10-bit analog-to-digital converter (ADC) that allows higher vertical resolution of signals captured at ultra-high bandwidth, and more than one maximum bandwidth input channel per oscilloscope to enable tight channel synchronization.
Keysight says it is using InP to get the higher bandwidths because engineers working with next-generation, high-speed interfaces, such as the upcoming IEEE P802.3bs 400G, as well as terabit coherent optical modulation, will need super-fast oscilloscopes for electrical parametric measurements. These technologies and others will play a key role in validating fifth-generation wireless (5G) designs. And these interfaces will drive the need for high-performance, real-time and equivalent-time signal analysis capabilities to 100 GHz and beyond. As data rates continue to extend beyond 56 Gb/s NRZ and 56 GBaud multi-level signaling, engineers will need not only higher bandwidth, but also higher vertical resolution and lower noise floors to address their validation challenges, and the new chipsets have been designed with this in mind.
Six years ago, Keysight released its first oscilloscope with chipsets built in the company’s proprietary InP semiconductor process. Keysight says it is still the only company that produces oscilloscopes made with InP chipsets.
“Keysight is investing in a completely new technology chain to meet the next-generation measurement needs of our customers,” said Dave Cipriani, vice president and general manager of Keysight’s oscilloscope business. “Our goal is to move multiple performance parameters ahead simultaneously. The next-generation oscilloscopes deliver bandwidths starting at 80 GHz and going beyond 100 GHz. They will have a lower noise density, providing higher-resolution measurements in tightly-synchronized, multi-channel systems. Whether customers are measuring higher baud rates, higher order QAM signals or multi-channel systems, these next-generation scopes will meet their needs.”
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