The Bandgap Engineer’s Periodic Table
In contrast with an elemental semiconductor such as Silicon, III-V Semiconductor compounds do not occur in nature and are instead combinations of materials from the III and V category groups on the periodic table. Silicon, although a proven as a functional semiconductor for electronic applications at lower frequencies is unable to perform a number of roles that III-V semiconductors are able to. This is in large part due to the indirect bandgap quality of Silicon. III-V semiconductor materials under a number of applications and combinations are direct bandgap semiconducting materials. This allows for operation at much higher speeds. Indirect bandgap materials will be unable to produce light.
Ternary and Quaternary III-V
The following list introduces the main III-V semiconductor material compounds used today. In a follow-up discussion, ternary and quarternary III-V semiconductors will be discussed in greater depth. To begin however, these may be understood as a process of mixing, varying or transitioning between two or more material types. For instance, a transition region between GaAs and GaP is described as GaAsxP1-x. This is the compound GaAsP, a blend of both GaAs and GaP, but at end of the material region, it is GaAs and at the other end it is equal to GaP.
GaAs was the first III-V material to play a major role in photonics. The first LED was fabricated using this material in 1961. GaAs is frequently used in microwave frequency devices and monolithic microwave integrated circuits. GaAs is used in a number of optical and optoelectronic near-infra-red range devices. The bandgap wavelength is λg = 0.873 μm.
Not long after GaAs was used, other III-V semiconductor materials were grown, such as GaSb. The bandgap wavelength of GaSb λg = 1.70 μm, making it useful for operation in the Infra-red band. GaSb can be used for infrared detectors, LEDs, lasers and transistors.
Similar to GaAs, Indium Phosphide is used in high-frequency electronics, photonic integrated circuits and optoelectronics. InP is widely used in the optical telecommunications industry for wavelength-division multiplexing applications. It is also used in photovoltaics.
An alloy of GaAs and GaP, Gallium Arsenide Phosphide is used for the manufacture of red, orange and yellow LEDs.
Indium Gallium Arsenide is used in high-speed and high sensitivity photodetectors and see common use in optical fiber telecommunications. InGaAs is an alloy often written as GaxIn1-xAs when defining compositions. The bandgap energy is approximately 0.75 eV, which is convenient for longer wavelength optical domain detection and transmission.
Indium Gallium Arsenide Phosphide is commonly used to create quantum wells, waveguides and other photonic structures. InGaAsP can be lattice-matched to InP well, which is the most common substrate material for photonic integrated circuits.
Indium Gallium Arsenide Antimonide has a narrow bandgap (0.5 eV to 0.6 eV), making it useful for the absorption of longer wavelengths. InGaAsSb faces a number of difficulties in manufacture and can be expensive to make, although when these difficulties are avoided, devices (such as photovoltaics) that use it may achieve high quantum efficiency (~90%).
Aluminum Gallium Aresinide has nearly the same lattice constant as GaAs, but with a larger bandgap, between 1.42 eV and 2.16 eV. AlGaAs may be used as part of a border region of a quantum well with GaAs as the inner section.
AlInGaP sees wide use in the construction of diode lasers and LEDs from deep ultraviolet to infrared ranges.
GaN has a wide bandgap of 3.4 eV and sees use in high frequency high power devices and optoelectronics. GaN transistors operate at higher voltages than the GaAs microwave transistors and sees possible use in THz devices.
InxGa1−xN is another ternary III-V semiconductor that can be tuned for use in optoelectronics from the ultraviolet (see GaN) to infrared (see InN) wavelengths.
AlxGa1−xN is another compound that sees use in LEDs for blue to ultraviolet wavelengths.
Although AlInGaN is not used much independently, it sees wide use in lattice matching the compounds GaN and AlGaN.
Indium Antimonide is an interesting compound, given that it has a very narrow bandgap of 0.17 eV and the highest electron mobility of any known semiconductor. InSb can be used in quantum wells and bipolar transistors operating up to 85 GHz and field-effect transistors operating at higher frequencies. It can also be used as a terrahertz radiation source.