Formosa Epitaxy Incorporation

Industrial Technology Research Institute

Ru-Chin Tu

Fen-Ren Chien

Liang-Wen Wu

Tzu-Chi Wen

Cheng-Tsang Yu

Jenq-Dar Tsay

Jung-Tsung Hsu

Shyi-Ming Pan

A structure for a gallium-nitride (GaN) based ultraviolet photo detector is provided. The structure contains an n-type contact layer, a light absorption layer, a light penetration layer, and a p-type contact layer, sequentially stacked on a substrate from bottom to top in this order. The layers are all made of aluminum-gallium-indium-nitride (AlGaInN) compound semiconductors. By varying the composition of aluminum, gallium, and indium, the layers, on one hand, can achieve the desired band gaps so that the photo detector is highly responsive to ultraviolet lights having specific wavelengths. On the other hand, the layers have compatible lattice constants so that problems associated with excessive stress are avoided and high-quality epitaxial structure is obtained. The structure further contains a positive electrode, a light penetration contact layer, and an anti-reflective coating layer on top of the p-type contact layer, and a negative electrode on the n-type contact layer.

Gallium-nitride based ultraviolet photo detector

An epitaxial structure for GaN-based LEDs to achieve better reverse withstanding voltage and anti-ESD capability is provided. The epitaxial structure has an additional anti-ESD thin layer on top of the p-type contact layer within traditional GaN-based LEDs, which is made of undoped indium-gallium-nitrides (InGaN) or low-band-gap (Eg&#x3c;3.4 eV), undoped aluminum-indium-gallium-nitrides (AlInGaN). This anti-ESD thin layer greatly improves the GaN-based LEDs' reverse withstanding voltage and resistivity to ESD, which in turn extends the GaN-based LEDs' operation life significantly.

Gallium-nitride based light-emitting diode structure with high reverse withstanding voltage and anti-ESD capability

A GaN-based LED structure is provided so that the brightness and lighting efficiency of the GaN-based LED are enhanced effectively. The greatest difference between the GaN-based LEDs according to the invention and the prior arts lies in the addition of a thin layer on top of the p-type contact layer within the traditional structure. The thin layer could be formed using silicon-nitride (SiN), or it could have a superlattice structure made of either SiN and undoped indium-gallium-nitride (InGaN), or SiN and undoped aluminum-gallium-indium-nitride (AlGaInN), respectively. Because of the use of SiN in the thin layer, the surfaces of the GaN-based LEDs would be micro-roughened, and the total internal reflection resulted from the GaN-based LEDs' higher index of refraction than the atmosphere could be avoided. The GaN-based LEDs according to the invention therefore have superior external quantum efficiency and lighting efficiency.

High-brightness gallium-nitride based light emitting diode structure

Disclosed is a GaN LED structure with a p-type contacting layer using Al&#x2014;Mg-codoped InGaN grown at low temperature, and having low resistivity. The LED structure comprises, from the bottom to top, a substrate, a buffer layer, an n-type GaN layer, an active layer, a p-type shielding layer, and a p-type contacting layer. In this invention, Mg and Al are used to co-dope the InGaN to grow a low resistive p-type contacting layer at low temperature. Because of the Al&#x2014;Mg-codoped, the light absorption problem of the p-type InGaN layer is improved. The product, not only has the advantage of convenience of the p-type contacting layer for being manufactured at low temperature, but also shows good electrical characteristics and lowers the operating voltage of the entire element so that the energy consumption during operation is reduced and the yield rate is increased.

GaN LED structure with p-type contacting layer grown at low-temperature and having low resistivity

Disclosed is a multi-quantum-well light emitting diode, which makes enormous adjustments and improvements over the conventional light emitting diode, and further utilizes a transparent contact layer of better transmittance efficiency, so as to significantly raise the illuminance of this light emitting diode and its light emission efficiency. The multi-quantum-well light emitting diode has a structure including: substrate, buffer layer, n-type gallium-nitride layer, active light-emitting-layer, p-type cladding layer, p-type contact layer, barrier buffer layer, transparent contact layer, and the n-type electrode layer.

Gallium-nitride based light emitting diode structure with enhanced light illuminance

A gallium-nitride based light-emitting diode structure includes a digital penetration layer to raise its reverse withstanding voltage and electrostatic discharge. The digital penetration layer is formed by alternate stacking layers of AlInGaNP/AlInGaNP, wherein 0&#x2266;x,y,z,p,q,r&#x2266;1, and AlInGaNPhas an energy gap greater than that of AlInGaNP. The AlInGaNPlayers have increasing thickness and the AlInGaNPlayers have decreasing thickness.

Light-emitting diode structure

A GaN-based LED structure is provided so that the brightness and luminous efficiency of the GaN-based LED are enhanced effectively. The greatest difference between the GaN-based LEDs according to the invention and the prior arts lies in the addition of a masking buffer layer on top of the p-type contact layer and a p-type roughened contact layer on top of the masking buffer layer. The masking buffer layer could be formed using MOCVD to deposit SiN(x,y&#x2267;1), MgN(w,z&#x2267;1), or AlInGaN (0&#x2266;s,t&#x3c;1, s+t&#x2266;1) heavily doped with Si and/or Mg. The masking buffer layer is actually a mask containing multiple randomly distributed clusters. Then, on top of the masking buffer layer, a p-type roughened contact layer made of p-type AlInGaN (0&#x2266;u,v&#x3c;, u+v&#x2266;) is developed. The p-type roughened contact layer does not grow directly on top of the masking buffer layer. Instead, the p-type roughened contact layer starts from the top surface of the underlying p-type contact layer not covered by the masking buffer layer's clusters. The p-type roughened contact layer then grows upward until it passes (but does not cover) the mask of the masking buffer layer for a specific distance. The total internal reflection that could have been resulted from the GaN-based LEDs' higher index of refraction than that of the atmosphere could be avoided. The GaN-based LEDs according to the present invention therefore have superior external quantum efficiency and luminous efficiency.

A structure for the n-type contact layer in the GaN-based MQW LEDs is provided. Instead of using Si-doped GaN as commonly found in conventional GaN-based MQW LEDs, the n-type contact layer provided by the present invention achieves high doping density (&#x3e;1&#xd7;10cm) and low resistivity through a superlattice structure combining two types of materials, AlInGaN and AlInGaN (0&#x2266;m,n&#x3c;1, 0&#x3c;p,q&#x3c;1, p+q&#x2266;1, m&#x3c;p), each having its specific composition and doping density. In addition, by controlling the composition of Al, In, and Ga in the two materials, the n-type contact layer would have a compatible lattice constant with the substrate and the epitaxial structure of the GaN-based MQW LEDs. This n-type contact layer, therefore, would not chap from the heavy Si doping, have a superior quality, and reduce the difficulties of forming n-type ohmic contact electrode. In turn, the GaN-based MQW LEDs would require a lower operation voltage.

Gallium-nitride based multi-quantum well light-emitting diode n-type contact layer structure

A GaN LED structure with a short period superlattice digital contacting layer is provided. The LED structure comprises, from the bottom to top, a substrate, a double buffer layer, an n-type GaN layer, a short period superlattice digital contacting layer, an active layer, a p-type shielding layer, and a contacting layer. The feature is to avoid the cracks or pin holes in the thick n-type GaN layer caused during the fabrication of heavily doped (n&#x3e;1&#xd7;10cm) thick n-type GaN contacting layer, so that the quality of the GaN contacting layer is assured. In addition, by using short period heavily doped silicon AlGaInN (n-AlGaInN) to grow a superlattice structure to become a short period superlattice digital contacting layer structure, which is used as a low resistive n-type contacting layer in a GaInN/GaN MQW LED. In the following steps, it is easier to form an n-type ohmic contacting layer, and the overall electrical characteristics are improved. It also lowers the operating voltage of the entire element so that the energy consumption during operation is reduced and the yield rate is increased.

Structure of GaN light-emitting diode

An epitaxial structure for the GaN-based LED is provided. The GaN-based LED uses a substrate usually made of sapphire or silicon-carbide (SiC). On top of the substrate, the GaN-based LED contains an n-type contact layer made of an n-type GaN-based material. On top of the n-type contact layer, the GaN-based LED further contains a lower barrier layer covering part of the surface of the n-type contact layer. A negative electrode is also on top of and has an ohmic contact with the n-type contact layer in an area not covered by the lower barrier layer. On top of the lower barrier layer, the GaN-based LED then further contains an active layer made of aluminum-gallium-indium-nitride, an upper barrier layer, a p-type contact layer made of a magnesium (Mg)-doped GaN material, and a positive electrode having an ohmic contact with the p-type contact layer, sequentially stacked in this order from bottom to top. Within this structure, each of the barrier layers further contains, from bottom to top, a first AlGaInN layer, a SiN layer, and a second AlGaInN layer.

Gallium-nitride based light-emitting diode epitaxial structure

The specification discloses a light-emitting diode and the corresponding manufacturing method. A GaN thick film with a slant surface is formed on the surface of a substrate. An epitaxial slant surface is naturally formed using the properties of the GaN epitaxy. An LED structure is grown on the GaN thick film to form an LED device. This disclosed method and device can simplify the manufacturing process. The invention further uses the GaN thick film epitaxial property to make various kinds of LED chips with multiple slant surfaces and different structures. Since the surface area for emitting light on the chip increases and the multiple slant surfaces reduce the chances of total internal reflections, the light emission efficiency of the invention is much better than the prior art.

Growing community of inventors

Tainan, Taiwan

Ru-Chin Tu