Basic knowledge of LED chip principles and classification

1. History of LED 50 years ago, people already knew the basic knowledge that semiconductor materials can generate light. In 1962, Nick Holonyak Jr. of General Electric developed the first practical visible light emitting diode. LED is the abbreviation of light emitting diode. Its basic structure is a piece of electroluminescent semiconductor material, placed on a frame with leads, and then sealed with epoxy resin on all sides, that is, solid packaging, so it can protect the internal core wire, so LED has good shock resistance. Initially, LED was used as an indicator light source for instruments and meters. Later, LEDs of various colors were widely used in traffic lights and large-area display screens, which produced good economic and social benefits. Take the 12-inch red traffic light as an example. In the United States, a long-life, low-efficiency 140-watt incandescent lamp was originally used as the light source, which produced 2,000 lumens of white light. After passing through the red filter, 90% of the light is lost, leaving only 200 lumens of red light. In the newly designed lamp, Lumileds uses 18 red LED light sources, including circuit losses, and consumes a total of 14 watts of power to produce the same light effect. Car signal lights are also an important application area for LED light sources.

2. The principle of LED chip: LED (Light Emitting Diode), a light-emitting diode, is a solid-state semiconductor device that can directly convert electricity into light. The heart of LED is a semiconductor chip. One end of the chip is attached to a bracket, one end is the negative pole, and the other end is connected to the positive pole of the power supply, so that the entire chip is encapsulated by epoxy resin. The semiconductor chip consists of two parts, one part is a P-type semiconductor, in which holes dominate, and the other end is an N-type semiconductor, which is mainly electrons. But when these two semiconductors are connected, a "PN junction" is formed between them. When the current acts on the chip through the wire, the electrons will be pushed to the P area, where the electrons and holes recombine, and then they will emit energy in the form of photons. This is the principle of LED luminescence. The wavelength of light, that is, the color of light, is determined by the material that forms the PN junction.

3. Classification of LED chips:

1. Definition and Features of MB Chip Definition: Metal Bonding chip; this chip is a patented product of UEC. Features: (1) It uses Si, a material with high heat dissipation coefficient, as the substrate, which is easy to dissipate heat. Thermal Conductivity GaAs: 46W/mK GaP: 77W/mK Si: 125～150W/mK Cupper: 300~400W/mk SiC: 490W/mK (2) The epitaxial layer and the substrate are bonded (wafer bonding) by a metal layer, while reflecting photons to avoid absorption by the substrate. (3) The conductive Si substrate replaces the GaAs substrate, which has good thermal conductivity (thermal conductivity is 3~4 times different) and is more suitable for the field of high drive current. (4) The bottom metal reflective layer is conducive to the improvement of light intensity and heat dissipation. (5) The size can be increased and applied to the Highpower field, eg: 42milMB.

2. Definition and Features of GB Chip Definition: GlueBonding chip; this chip is a patented product of UEC. Features: (1) The transparent sapphire substrate replaces the light-absorbing GaAs substrate, and its light output power is more than twice that of the traditional AS (Absorbable structure) chip. The sapphire substrate is similar to the GaP substrate of the TS chip. (2) The chip emits light on all four sides and has an excellent pattern. (3) In terms of brightness, its overall brightness has exceeded the level of TS chips (8.6mil). (4) With a dual-electrode structure, its high current resistance is slightly worse than that of the TS single-electrode chip.

3. TS chip definition and features Definition: transparent structure chip, this chip is a patented product of HP. Features: (1) The chip manufacturing process is complex, far higher than ASLED. (2) Excellent reliability. (3) Transparent GaP substrate, does not absorb light, high brightness. (4) Widely used.

4. Definition and characteristics of AS chips Definition: Absorbable structure (absorbent substrate) chip; after nearly 40 years of development efforts, Taiwan's LED optoelectronics industry has reached a mature stage in the research and development, production and sales of this type of chip. The research and development levels of major companies in this regard are basically at the same level, with little difference. The mainland chip manufacturing industry started late, and its brightness and reliability are still a certain distance away from the Taiwan industry. The AS chips we are talking about here refer specifically to UEC's AS chips, eg: 712SOL-VR, 709SOL-VR, 712SYM-VR, 709SYM-VR, etc. Features: (1) Four-element chip, prepared using MOVPE process, brighter than conventional chips. (2) Excellent reliability. (3) Widely used.
4. Types of epitaxy of light-emitting diode chip materials 1. LPE: Liquid Phase Epitaxy (liquid phase epitaxy) GaP/GaP 2. VPE: Vapor Phase Epitaxy (vapor phase epitaxy) GaAsP/GaAs 3. MOVPE: Metal Organic Vapor Phase Epitaxy (metal organic vapor phase epitaxy) AlGaInP, GaN 4. SH: GaAlAs/GaAs Single Heterostructure (single heterostructure) GaAlAs/GaAs 5. DH: GaAlAs/GaAs Double Heterostructure (double heterostructure) GaAlAs/GaAs 6. DDH: GaAlAs/GaAlAs Double Heterostructure (double heterostructure) GaAlAs/GaAlAs

5. Composition of LED chips and light-emitting diode chips: mainly composed of several elements including arsenic (AS), aluminum (AL), gallium (Ga), indium (IN), phosphorus (P), nitrogen (N), and strontium (Si).

Classification of LED chips:

1. According to the brightness of light: A. General brightness: R, H, G, Y, E, etc. B. High brightness: VG, VY, SR, etc. C. Ultra-high brightness: UG, UY, UR, UYS, URF, UE, etc. D. Invisible light (infrared): R, SIR, VIR, HIR E. Infrared receiving tube: PT F. Photoelectric tube: PD

2. According to the composition elements: A. Binary chips (phosphorus, gallium): H, G, etc. B. Ternary chips (phosphorus, gallium, arsenic): SR, HR, UR, etc. C. Quaternary chips (phosphorus, aluminum, gallium, indium): SRF, HRF, URF, VY, HY, UY, UYS, UE, HE, UG

3. LED chip characteristics table: LED chip model Luminous color Composition elements Wavelength (nm) SBI Blue lnGaN/sic430HY Super bright yellow AlGalnP595 SBK Brighter blue lnGaN/sic468SE High bright orange GaAsP/GaP610 DBK Brighter blue GaunN/Gan470HE Super bright orange AlGalnP620 SGL Cyan lnGaN/sic502UE Brightest orange AlGalnP620 DGL Brighter Cyan LnGaN/GaN505URF Brightest red AlGalnP630 DGM Brighter Cyan lnGaN523E Orange GaAsP/GaP635 PG Pure green GaP555R Red GAaAsP655 SG Standard green GaP560SR Brighter red GaA/AS660 G Green GaP565HR Super bright red GaAlAs660 VG brighter green GaP565UR brightest red GaAlAs660 UG brightest green AIGalnP574H high red GaP697 Y yellow GaAsP/GaP585HIR infrared GaAlAs850 VY brighter yellow GaAsP/GaP585SIR infrared GaAlAs880 UYS brightest yellow AlGalnP587VIR infrared GaAlAs940 UY brightest yellow AlGalnP595IR infrared GaAs940