Hydride vapour-phase epitaxy

Hydride vapour phase epitaxy (HVPE) is an epitaxial growth technique often employed to produce semiconductors such as GaN, GaAs, InP and their related compounds. Carrier gasses commonly used include ammonia, hydrogen and various chlorides.

[1]

In the HVPE process, Group III nitrides (e.g., GaN, AlN) are formed by reacting hot gaseous metal chlorides (e.g., GaCl or AlCl) with ammonia gas (NH3) (Refer to diagram below). The metal chlorides are generated by passing hot HCl gas over the hot Group III metals. All reactions are done in a temperature controlled quartz furnace.

e.g., Hot HCl (g) + Ga (l) ------> GaCl (g) GaCl (g) + NH3 (g) -------> GaN (s) + HCl (g) + H2 (g)

The GaN or AlN templates have been grown on substrates such as SiC or sapphire. p-type GaN or AlN can be achieved by using Mg during the process and n-type by silane gas with Argon as the carrier gas.

Advantages of HVPE

Developed in the 1960s, it was the first epitaxial method used for the fabrication of single GaN crystals. One of the key features of the technique is its high growth rate (at up to 100 µm per hour) which is almost two orders of magnitude faster than typical MOCVD and MBE processes.

The technique is able to produce crack-free, high quality GaN epitaxial layers (e.g., a typical dislocation density can be as low as 107/cm3 for a 10 µm thick GaN template on sapphire.) Figure 1 shows the X-ray diffraction of a 10 µm thick GaN template on sapphire. The narrow FWHM of 250 arcsec measured at w-scan (0002) peak demonstrates excellent material quality.

Another advantage of HVPE is its ability to grow thick, high quality of AlGaN and AlN for use in optoelectronic and RF electronic devices. The technique has been demonstrated by TDI to grow thicker high quality AlGaN-based active regions of shorter wavelength emitters, which have a high radiative recombination efficiency – an essential feature for high-efficiency UV LEDs. Unlike MOCVD, the HVPE process does not involve metalorganics, thus providing a ‘carbon-free’ environment for epitaxial growth. In addition, the use of gaseous hydrogen chloride also provides an impurity ‘self-cleaning’ effect, which results in epitaxial layers with low background impurities and more efficient doping level.

TDI has demonstrated the industry’s first HVPE-grown, multilayer, submicron AlGaN/GaN heterostructures.

InGaN is one of the key compound semiconductor materials used for the fabrication of GaN-based blue, green and white LEDs and blue laser diodes. Most of the existing LEDs reply on MOCVD to produce the quantum well structures for the InGaN emitters. Recently, TDI has developed the HVPE technology to control the growth of InGaN to very low levels of about 0.5 to 1 µm per hour needed to make quantum wells structures.

The development of InGaN materials, for the first time, will allow the fabrication of blue and green LEDs using the HVPE method, and TDI has recently been awarded a significant funding by the DARPA VIGIL program to develop green laser technology based on InGaN-GaN materials. © 2007-2008 Technoinfo Ltd.

разработка сайта: sitefactor.ru