Defining an optimal plasma processing toolkit for
Indium Phosphide (InP) laser diode production
The properties of InP which combine a wide band gap with high electron mobility, make it a desirable
semiconductor for the manufacture of optoelectronic devices. A key application is communication and this is
expanding rapidly with increased data traffic.
InP enables the manufacture of components that can operate at high frequencies allowing higher volumes of
data. In particular it offers compelling advantages for laser diode manufacture delivering excellent
functionality at a competitive price. When design and fabrication is optimised InP lasers provide high
spectral purity and optical power, over a wide temperature range. Furthermore the achievable wavelength
range of 1100 – 2000 nm is optimal for fibre optic communications. Establishing cost-effective processing
strategies for the production of InP lasers therefore directly supports the advancement of communications to
support the ever increasing demand for data transfer.
In this white paper we examine the role of plasma processing technologies in InP laser diode manufacture
focusing on the relative merits of inductively coupled plasma chemical vapour deposition (ICPCVD), plasma
enhanced CVD (PECVD), reactive ion etching (RIE) and ICP-RIE. A primary aim is to highlight the relevant
characteristics of different processes and show how they can be optimally applied, in combination, to
efficiently fabricate high performance lasers.
Understanding InP laser diodes
In a laser diode, photons are spontaneously emitted when an electron and a hole recombine and interact
with incoming electrons to produce more photons, propagating the process of resonance which ultimately
produces a collimated laser beam. Direct band gap semiconductors such as InP with atomic structures that
allow for the possibility of photon emissions are clearly a prerequisite for such devices. However the
properties of the resulting laser, in particular its wavelength, are influenced not only by the band gap of the
semiconductor but also by the physical structure of the device. Waveguides and gratings play an essential
role in amplifying the light and controlling the wavelength band of the resulting laser.
Figure 1: InP laser
structure with a. surface
distributed feedback and
b. buried distributed
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