Updated July 19, 2009

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Indium phosphide is like the weird uncle of gallium arsenide. It has some quirks, including being very brittle, and it costs more than GaAs. But some of the highest frequencies of operation reported are on InP, so it will always serve a niche as systems move toward terahertz. GaAs MHEMT can be tailored to behave almost like InP, which provides a path toward cheaper production.

This page so far has two topics:

Indium phosphide HEMT

Indium phosphide HBT

Indium phosphide (InP) HEMT

Indium phosphide HEMT has broken all of the upper frequency records, on the way to terahertz devices. However, there are serious drawbacks to this technology, not the least of which is its high cost. For this reason, InP is more regarded as a lab curiosity rather than a production process.

The actual semiconductor that is doing the work in so-called InP is actually InGaAs. Indium phosphide is merely the substrate that it is grown onto. The reason for this is that InGaAs shares the same lattice constant with InP, 5.87 angstroms.

InP substrates are small (3" typical, 4" are available but remember bigger is not always better when something is brittle). ER=12.4, close to that of GaAs. A huge drawback of indium phosphide technology is that InP wafers are extremely brittle compared to other semiconductors. Try shipping an InP wafer sometime. Silicon is the least brittle (think Frisbee!), and GaAs is somewhere in the middle.

Examples:

Northrop Grumman

Indium phosphide (InP) HBT

Some people think that InP will have a second chance to become the most ubiquitous power amplifier technology for cell phones when new higher power density/lower voltage lithium ion batteries become available, as suggested in this December 2006 High Frequency Electronics article by Michael Gaynor. Here the author claims that InP has superior low voltage power/efficiency performance compared to GaAs HBT.

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