Индий-галлий арсенидінің қасиеттері мен қолданылуы

Alloy

Indium gallium arsenide (InGaAs) (alternatively gallium indium arsenide, GaInAs) is a ternary alloy (chemical compound) of indium arsenide (InAs) and gallium arsenide (GaAs). Indium and gallium are group III elements of the periodic table while arsenic is a group V element. Alloys made of these chemical groups are referred to as "III V" compounds. InGaAs has properties intermediate between those of GaAs and InAs. InGaAs is a room temperature semiconductor with applications in electronics and photonics. The principal importance of GaInAs is its application as a high speed, high sensitivity photodetector of choice for optical fiber telecommunications.

Indium gallium arsenide (InGaAs) and gallium indium arsenide (GaInAs) are used interchangeably. According to IUPAC standards the preferred nomenclature for the alloy is GaxIn1 xAs where the group III elements appear in order of increasing atomic number, as in the related alloy system AlxGa1 xAs. By far, the most important alloy composition from technological and commercial standpoints is Ga0.47In0.53As, which can be deposited in single crystal form on indium phosphide (InP).

GaInAs is not a naturally occurring material. Single crystal material is required for electronic and photonic device applications. Pearsall and co workers were the first to describe single crystal epitaxial growth of In0.53Ga0.47As on (111) oriented and on (100) oriented InP substrates. Single crystal material in thin film form can be grown by epitaxy from the liquid phase (LPE), vapour phase (VPE), by molecular beam epitaxy (MBE), and by metalorganic chemical vapour deposition (MO CVD). Today, most commercial devices are produced by MO CVD or by MBE. The optical and mechanical properties of InGaAs can be varied by changing the ratio of InAs and GaAs, Most InGaAs devices are grown on indium phosphide (InP) substrates. In order to match the lattice constant of InP and avoid mechanical strain, is used. This composition has an optical absorption edge at 0.75 eV, corresponding to a cut off wavelength of λ=1.68 μm at 295 K.

By increasing the mole fraction of InAs further compared to GaAs, it is possible to extend the cut off wavelength up to about λ=2.6 μm. In that case special measures have to be taken to avoid mechanical strain from differences in lattice constants. GaAs is lattice mismatched to germanium (Ge) by 0.08%. With the addition of 1.5% InAs to the alloy, In0.015Ga0.985As becomes latticed matched to the Ge substrate, reducing stress in subsequent deposition of GaAs.

InGaAs has a lattice parameter that increases linearly with the concentration of InAs in the alloy. The liquid solid phase diagram]]

The bandgap energy of GaInAs can be determined from the peak in the photoluminescence spectrum, provided that the total impurity and defect concentration is less than 5 cm−3. The bandgap energy depends on temperature and increases as the temperature decreases, as can be seen in Fig. 3 for both n type and p type samples. The bandgap energy at room temperature for standard InGaAs/InP (53% InAs, 47% GaAs), is 0.75 eV and lies between that of Ge and Si. By coincidence the bandgap of GaInAs is perfectly placed for photodetector and laser applications for the long wavelength transmission window, (the C band and L band) for fiber optic communications.

The electron effective mass of GaInAs m*/m° = 0.041
The electrical and optical properties of the valence band are dominated by the heavy holes, because the density of these states is much greater than that for light holes. This is also reflected in the mobility of holes at 295 K, which is a factor of 40 lower than that for electrons.

The principal application of GaInAs is as an infrared detector. The spectral response of a GaInAs photodiode is shown in Figure 5. GaInAs photodiodes are the preferred choice in the wavelength range of 1.1 μm < λ < 1.7 μm. For example, compared to photodiodes made from Ge, GaInAs photodiodes have faster time response, higher quantum efficiency and lower dark current for the same sensor area. GaInAs photodiodes were invented in 1977 by Pearsall. Avalanche photodiodes offer the advantage of additional gain at the expense of response time. These devices are especially useful for detection of single photons in applications such as quantum key distribution where response time is not critical. Avalanche photodetectors require a special structure to reduce reverse leakage current due to tunnelling. The first practical avalanche photodiodes were designed and demonstrated in 1979. In 1980, Pearsall developed a photodiode design that exploits the uniquely short diffusion time of high mobility of electrons in GaInAs, leading to an ultrafast response time. This structure was further developed and subsequently named the UTC, or uni travelling carrier photodiode. In 1989, Wey and co workers designed and demonstrated a p i n GaInAs/InP photodiodes with a response time shorter than 5 picoseconds for a detector surface measuring 5 μm x 5 μm. Other important innovations include the integrated photodiode – FET receiver and the engineering of GaInAs focal plane arrays.

Semiconductor lasers are an important application for GaInAs, following photodetectors. GaInAs can be used as a laser medium. Devices have been constructed that operate at wavelengths of 905 nm, 980 nm, 1060 nm, and 1300 nm. InGaAs quantum dots on GaAs have also been studied as lasers. GaInAs/InAlAs quantum well lasers can be tuned to operate at the λ = 1500 nm low loss, low dispersion window for optical fiber telecommunications
In 1994, GaInAs/AlInAs quantum wells were used by Jérôme Faist and co workers who invented and demonstrated a new kind of semiconductor laser based on photon emission by an electron making an optical transition between subbands in the quantum well. They showed that the photon emission regions can be cascaded in series, creating the quantum cascade laser (QCL). The energy of photon emission is a fraction of the bandgap energy. For example, GaInAs/AlInAs QCL operates at room temperature in the wavelength range 3 μm < λ < 8 μm. The wavelength can be changed by modifying the width of the GaInAs quantum well. These lasers are widely used for chemical sensing and pollution control.