FREQUENTLY ASKED QUESTIONS
What is RPCVD?
Remote plasma chemical vapour deposition works in a similar way to MOCVD (see below) where chemicals are introduced into the reaction chamber for decomposition.
Whereas MOCVD uses ammonia (NH3) as the source of nitrogen, RPCVD uses nitrogen gas (N2) passed through an electrical coil that generates a plasma. This arrangement provides a direct source of nitrogen used for the deposition of GaN.
The nitrogen plasma generation is not dependent on high temperature to provide a source of reactive nitrogen atoms. This allows for the growth of GaN to be carried out at much lower temperatures than those used in MOCVD while maintaining the critical crystalline quality necessary for high performance devices. Nitrogen is safer to handle and does not require scrubbing compared to highly toxic ammonia used in MOCVD.
What is MOCVD?
MOCVD is a method used to deposit (grow) semiconductor films onto a substrate (wafer). When producing gallium nitride (GaN) organometallic compounds are reacted with ammonia inside a deposition chamber. This gas mixture is precisely delivered to a heated substrate (up to approximately 1,200°C).
The precursor molecules undergo pyrolysis (thermal decomposition) leaving the desired atoms, e.g., Ga and N. These atoms bond at the surface and crystalline layers of GaN are formed in neatly stacked layers.
For the growth of GaN, MOCVD uses ammonia (NH3) as the nitrogen source. MOCVD relies on very high temperature to effectively break the nitrogen-hydrogen bonds to result in a quality deposition.
What is an LED?
A light emitting diode is a semiconductor light that when switched on, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the colour of the light (corresponding to the energy of the photon) is determined by the band gap of the semiconductor. An LED is often small in area (less than 1 mmsq), LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching.
What is GaN?
Gallium nitride is a group III nitride semiconductor material with a direct bandgap. It is commonly used in number of optoelectronic and power electronic devices including light emitting diodes, lasers, transistors, blu-ray disks and memory devices. GaN is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronic, high-power and high-frequency devices. It is also a suitable material for solar cell arrays for satellites and utility scale concentrated photovoltaics.
What is InGaN?
Indium gallium nitride is a semiconductor material made of a mix of gallium nitride (GaN) and indium nitride (InN). It is a ternary group III/group V direct bandgap semiconductor. Its bandgap can be tuned by varying the amount of indium in the alloy. Indium gallium nitride is the light-emitting layer in modern blue and green LEDs. It has extreme tolerance to radiation, which combined with its highly tunable bandgap makes it a highly promising and durable solar photovoltaic material for ultra high efficient devices suitable for space and utility applications.
What is CPV?
Concentrated photovoltaics are a form of high efficiency solar power, usually for utility scale solar that concentrates through the use of mirrors or lenses a large amount of solar onto a smaller section of high efficiency solar material, concentrating the sunlight on the cell by up to several hundred times. CPV offers large scale, affordable renewable energy from the sun.
What is SSL?
Solid state lighting, refers to a type of lighting that uses various types of LED as sources of illumination. The term "solid state" refers commonly to light emitted by solid-state electroluminescence, as opposed to incandescent bulbs (which use thermal radiation) or fluorescent tubes. Semiconductor LEDs such as GaN based LEDs are the fastest growing technology for overhead lighting.
What is p-GaN?
p-GaN (or p-type GaN) refers to a GaN film that has been doped with certain types of atoms (such as magnesium), to increase the number of free charge carriers (in this case positive holes). Low temperature p-GaN is one area that BluGlass is presently focusing on.
What is n-GaN?
n-GaN (or n-type GaN) refers to a GaN film that has been doped with certain types of atoms (e.g. silicon) to increase the number of free charge carriers (in this case electrons)
What is a MQW?
A quantum well is a thin layer (typically between 1-10 nm thick) within which electrons and or holes are confined in the direction perpendicular to the layer surface. A quantum well is often realised with a thin layer of a semiconductor material, embedded between other semiconductor layers of higher bandgap materials (example: InGaN quantum well embedded between GaN layers). In a quantum well, the potential energy of electrons and or holes is less than their potential energy in the outer layers, so that electrons and or holes are confined within the layer (like a well) and their energy becomes quantised or discrete giving rise to many benefits, e.g. higher optical gain. A multiple quantum well (MQW) is a series of quantum wells, which is used in LEDs as the active region (that emits lights) in order to obtain a large optical gain.
What are the core advantages of RPCVD?
A low temperature growth system such as RPCVD may offer LED manufacturers compelling performance advantages at several stages of device growth.