论文部分内容阅读
On the 7th of October 2014， Isamu Akasaki， Hiroshi Amano and Shuji Nakamura were awarded the Nobel Prize in Physics for the invention of efficient blue lightemitting 1）diodes （LEDs）. Red and green LEDs were created in a number of laboratories during the 1950s and 60s but it took another three decades to finally produce efficient blue LEDs， which begs the question—why were they so hard to make？
Light-emitting diodes are electronic devices which are illuminated by the movement of 2）electrons in a 3）semiconductor material. LEDs are able to emit light with a range of wavelengths from the 4）infrared to the 5）ultraviolet.
A semiconductor is a material with an 6）electrical conductivity which is somewhere between a conductor such as copper， and an 7）insulator such as rubber. They are usually made from a poor conductor which is then “doped” by adding atoms of another material to it.
LEDs are typically made from aluminum-gallium-arsenide（AlGaAs） which in its pure form does not contain any free electrons to conduct electrical current. As a result， AlGaAs is doped with either free electrons or “8）electron holes” in order to change the material’s balance and make it more conductive.
Semiconductors can be classified into two types of material； N-type and P-type：
？ N-type semiconductors contain extra negatively charged electrons and， as a result， the free electrons flow from negatively charged areas to positively charged areas.？ P-type semiconductors have extra holes， allowing free electrons to jump between the holes and moving from negatively charged areas to positively charged areas as a result.
A diode consists of a section of an N-type semiconductor attached to a section of a P-type semiconductor （known as a p-n junction） with two 9）electrodes placed at either end of this arrangement. When current flows across a diode， the negatively charged electrons move in one direction in the material and the positively charged holes move in the opposite direction. As the holes exist in lower energy states， a free electron will lose energy when it falls to a hole and emit this energy in the form of a 10）photon of light.
The size of the fall in energy determines the energy the photon has when it is emitted， which in turns determines the colour of the light the diode emits. An emitted photon with a large amount of energy will have a shorter wavelength than light emitted with a lower amount of energy.
The first diode which was able to emit electrically produced light was created in 1907 by H.J. Round whilst he was experimenting with a 11）cat’s-whisker detector. Round applied a potential difference across a silicon carbide （SiC） crystal. He found that the colour of light emitted varied depending on the voltage which was applied across the crystal. During the 1920s and 1930s， the phenomena of 12）electroluminescence was studied by Soviet physicist who published several journal articles on the subject.
In 1947， the electronic 13）transistor was invented at Bell Telephone Laboratories thanks in part to the advancement in understanding of semiconductors and p-n junctions.
Infrared LEDs were created in 1962 using p-n junctions made from GaAs. By the end of the 1960s， red and green LEDs were being manufactured in different countries using p-n junctions made from GaP. The development of a blue LED however proved far more difficult to scientists.
The first attempts at the emission of blue light from a diode used ZnSe and SiC， but did not produce efficient light emission. The material which enabled the development of blue LEDs was gallium nitride （GaN）.
In 1974 Isamu Akasaki began studying gallium nitride and took up a professorship at Nagoya University to continue his research alongside Hiroshi Amano. In 1986 the 14）MOVPE technique was used in order to produce GaN with high crystal quality and good 15）optical properties. Shuji Nakamura later developed a similar method in order to grow GaN at low temperatures.
A key step in the development of blue LEDs was the development of 16）heterojunctions in the early 1990s by research groups led by Akasaki and Nakamura. In 1994， Nakamura used a double heterojunction InGaN/AlGaN to produce a device with a quantum efficiency of 2.7%， which opened the door for efficient blue LEDs to be easily produced.
Illumination technology is currently undergoing a major revolution， with light bulbs and 17）fluorescent tubes being replaced by LEDs. White LEDs currently have an energy efficiency of around 50% when converting electricity into light. This is a massive improvement on the 4% energy efficiency of conventional light bulbs which were first invented in 1879 by Thomas Edison.
White LEDs have lifetimes of around 100，000 hours and are quickly becoming more affordable as market demand increases. Replacing conventional light bulbs with LEDs will drastically reduce the planet’s energy requirement for light， as between 20% and 30% of the world’s electricity consumption is as a result of lighting.
Presently， LED technology is used in the back-lit screens of many mobile phones， laptops and television screens. Blue GaN diode lasers find applications in the technology which underpins the data storage on Blu-ray Discs， which are predicted to supersede DVDs. One day， AlGaN/GaN LEDs could find applications in water purification， as their UV light may be able to destroy viral and bacterial DNA. And for countries with poor electrical 18）infrastructure， many believe solar powered white LEDs will replace the use of kerosene lamps at night.
2014年10月7日，赤崎勇、天野浩和中村修二因发明了高效能的蓝色发光二极管（LED）而被授予诺贝尔物理学奖。红色和绿色的LED在上世纪五六十年代已经由多个实验室创造出来，但高效能的蓝色LED却要经历又一个三十年才最终被制造出来，这不禁让人心生疑问—为什么蓝色LED这么难造？
发光二极管是一种靠电流在半导体材料中流动而发光的电子器件。LED能够发出波长范围从红外线到紫外线的光。
半导体是一种导电性介乎铜导体和橡胶绝缘体之间的一种材料。通常是通过向某种导电性较差的导体中掺杂其它材料的原子制作而成。
LED一般用铝砷化镓做成，这种材料在其纯态时因不含任何自由电子而无法导电。于是，人们通过向铝砷化镓中掺入自由电子或“电子空穴”来改变材料的平衡，使之更具导电性。
半导体按材料类型可分成两种—N型和P型：
？ N型半导体带有额外的带负电荷的电子，因此，自由电子流就能从带负电荷的区域流向带正电荷的区域。
？ P型半导体带有额外的电子空穴，允许自由电子在电子空穴之间跳跃，从而实现从带负电荷的区域流向带正电荷的区域。
二极管由一块包含了N型半导体和P型半导体的基片（被称作PN结）以及位于该组合两端的电极组成。当电流通过二极管时，带负电荷的电子就会在材料中向某一方向移动，而带正电荷的空穴则会以反方向移动。由于电子空穴处于较低能阶，自由电子就会在掉入电子空穴时以光子的模式释放出能量。
能量落差的强度决定了光子释放出的光能强弱，继而决定了二极管发出的光的颜色。释放出的具有高能量的光子，其波长会比较低能量的光子短。
第一代能够通过电流发光的二极管是由H·J·朗德于1907年创造的，当时他正以一块晶体检波器进行实验。朗德在碳化硅晶体上接上不同电位差的电流。他发现晶体发出的光的颜色会随着所接电压的不同而发生变化。
在上世纪20年代及30年代间，苏联物理学家对电致发光的现象进行研究，并就该课题的研究成果发表了几篇期刊论文。
在1947年，贝尔电话实验室发明了电子晶体管，部分归功于对半导体组件和PN结的进一步理解。
红外线LED是在1962年使用由砷化镓材料做成的PN结而创造出来的。上世纪60年代末，红色和绿色的LED在不同的国家运用由磷化镓材料做成的PN结制造而成。然而蓝光LED的发展则一直是科学家们的难题。
最初，人们尝试用硒化锌和碳化硅来做发蓝光的二极管，但无法实现高效能的发光。促使蓝光LED的研发得以向前发展的材料是氮化镓。
在1974年，赤崎勇开始研究氮化镓，并且接受了名古屋大学的教授职位，与天野浩并肩继续其研究。到了1986年，金属有机物气相外延技术被应用来制造具有高晶体质量和优质光学性能的氮化镓。之后中村修二研发出一种类似的方法以实现低温环境下生成氮化镓。
在上世纪90年代初期，由赤崎和中村分别领导的研究组所取得的半导体异质结构研究成果是蓝光LED研究发展历程中的关键一步。1994年，中村使用双异质结氮化铟镓/氮化铝镓来制造一种具有2.7%量子效率的装置，继而为轻易制造出高效能蓝光LED打开了大门。
照明技术如今正在经历着一场重大的变革，电灯泡和荧光灯正逐渐被LED所取代。当前白光LED在电转光上能达到50%左右的能效。1879年，由托马斯·爱迪生发明的传统电灯泡仅具有4%的能效，两者相比，白光LED实在是巨大的进步。
白光LED的寿命约有十万小时，且其价格很快会因为市场需求的增长而愈趋合理。以LED取代传统的电灯泡将会大幅度降低因为照明所带来的对于地球的能源需求，目前全球电力消费的20%至30%都用于照明。
目前，LED技术用于众多手机、笔记本电脑和电视屏幕的背光屏幕中。蓝光氮化镓二极管激光器被应用于蓝光光盘的数据存储支撑技术上，人们预测蓝光光盘会取代DVD光盘。
将来会有一天，人们还会在水净化技术中看到氮化铟镓/氮化铝镓LED的应用，因为它们的紫外线能够破坏病毒和细菌的DNA。而对于那些电力设施比较落后的国家，人们相信太阳能驱动的白光LED将会替代煤油灯来照亮夜晚。
Light-emitting diodes are electronic devices which are illuminated by the movement of 2）electrons in a 3）semiconductor material. LEDs are able to emit light with a range of wavelengths from the 4）infrared to the 5）ultraviolet.
A semiconductor is a material with an 6）electrical conductivity which is somewhere between a conductor such as copper， and an 7）insulator such as rubber. They are usually made from a poor conductor which is then “doped” by adding atoms of another material to it.
LEDs are typically made from aluminum-gallium-arsenide（AlGaAs） which in its pure form does not contain any free electrons to conduct electrical current. As a result， AlGaAs is doped with either free electrons or “8）electron holes” in order to change the material’s balance and make it more conductive.
Semiconductors can be classified into two types of material； N-type and P-type：
？ N-type semiconductors contain extra negatively charged electrons and， as a result， the free electrons flow from negatively charged areas to positively charged areas.？ P-type semiconductors have extra holes， allowing free electrons to jump between the holes and moving from negatively charged areas to positively charged areas as a result.
A diode consists of a section of an N-type semiconductor attached to a section of a P-type semiconductor （known as a p-n junction） with two 9）electrodes placed at either end of this arrangement. When current flows across a diode， the negatively charged electrons move in one direction in the material and the positively charged holes move in the opposite direction. As the holes exist in lower energy states， a free electron will lose energy when it falls to a hole and emit this energy in the form of a 10）photon of light.
The size of the fall in energy determines the energy the photon has when it is emitted， which in turns determines the colour of the light the diode emits. An emitted photon with a large amount of energy will have a shorter wavelength than light emitted with a lower amount of energy.
The first diode which was able to emit electrically produced light was created in 1907 by H.J. Round whilst he was experimenting with a 11）cat’s-whisker detector. Round applied a potential difference across a silicon carbide （SiC） crystal. He found that the colour of light emitted varied depending on the voltage which was applied across the crystal. During the 1920s and 1930s， the phenomena of 12）electroluminescence was studied by Soviet physicist who published several journal articles on the subject.
In 1947， the electronic 13）transistor was invented at Bell Telephone Laboratories thanks in part to the advancement in understanding of semiconductors and p-n junctions.
Infrared LEDs were created in 1962 using p-n junctions made from GaAs. By the end of the 1960s， red and green LEDs were being manufactured in different countries using p-n junctions made from GaP. The development of a blue LED however proved far more difficult to scientists.
The first attempts at the emission of blue light from a diode used ZnSe and SiC， but did not produce efficient light emission. The material which enabled the development of blue LEDs was gallium nitride （GaN）.
In 1974 Isamu Akasaki began studying gallium nitride and took up a professorship at Nagoya University to continue his research alongside Hiroshi Amano. In 1986 the 14）MOVPE technique was used in order to produce GaN with high crystal quality and good 15）optical properties. Shuji Nakamura later developed a similar method in order to grow GaN at low temperatures.
A key step in the development of blue LEDs was the development of 16）heterojunctions in the early 1990s by research groups led by Akasaki and Nakamura. In 1994， Nakamura used a double heterojunction InGaN/AlGaN to produce a device with a quantum efficiency of 2.7%， which opened the door for efficient blue LEDs to be easily produced.
Illumination technology is currently undergoing a major revolution， with light bulbs and 17）fluorescent tubes being replaced by LEDs. White LEDs currently have an energy efficiency of around 50% when converting electricity into light. This is a massive improvement on the 4% energy efficiency of conventional light bulbs which were first invented in 1879 by Thomas Edison.
White LEDs have lifetimes of around 100，000 hours and are quickly becoming more affordable as market demand increases. Replacing conventional light bulbs with LEDs will drastically reduce the planet’s energy requirement for light， as between 20% and 30% of the world’s electricity consumption is as a result of lighting.
Presently， LED technology is used in the back-lit screens of many mobile phones， laptops and television screens. Blue GaN diode lasers find applications in the technology which underpins the data storage on Blu-ray Discs， which are predicted to supersede DVDs. One day， AlGaN/GaN LEDs could find applications in water purification， as their UV light may be able to destroy viral and bacterial DNA. And for countries with poor electrical 18）infrastructure， many believe solar powered white LEDs will replace the use of kerosene lamps at night.
2014年10月7日，赤崎勇、天野浩和中村修二因发明了高效能的蓝色发光二极管（LED）而被授予诺贝尔物理学奖。红色和绿色的LED在上世纪五六十年代已经由多个实验室创造出来，但高效能的蓝色LED却要经历又一个三十年才最终被制造出来，这不禁让人心生疑问—为什么蓝色LED这么难造？
发光二极管是一种靠电流在半导体材料中流动而发光的电子器件。LED能够发出波长范围从红外线到紫外线的光。
半导体是一种导电性介乎铜导体和橡胶绝缘体之间的一种材料。通常是通过向某种导电性较差的导体中掺杂其它材料的原子制作而成。
LED一般用铝砷化镓做成，这种材料在其纯态时因不含任何自由电子而无法导电。于是，人们通过向铝砷化镓中掺入自由电子或“电子空穴”来改变材料的平衡，使之更具导电性。
半导体按材料类型可分成两种—N型和P型：
？ N型半导体带有额外的带负电荷的电子，因此，自由电子流就能从带负电荷的区域流向带正电荷的区域。
？ P型半导体带有额外的电子空穴，允许自由电子在电子空穴之间跳跃，从而实现从带负电荷的区域流向带正电荷的区域。
二极管由一块包含了N型半导体和P型半导体的基片（被称作PN结）以及位于该组合两端的电极组成。当电流通过二极管时，带负电荷的电子就会在材料中向某一方向移动，而带正电荷的空穴则会以反方向移动。由于电子空穴处于较低能阶，自由电子就会在掉入电子空穴时以光子的模式释放出能量。
能量落差的强度决定了光子释放出的光能强弱，继而决定了二极管发出的光的颜色。释放出的具有高能量的光子，其波长会比较低能量的光子短。
第一代能够通过电流发光的二极管是由H·J·朗德于1907年创造的，当时他正以一块晶体检波器进行实验。朗德在碳化硅晶体上接上不同电位差的电流。他发现晶体发出的光的颜色会随着所接电压的不同而发生变化。
在上世纪20年代及30年代间，苏联物理学家对电致发光的现象进行研究，并就该课题的研究成果发表了几篇期刊论文。
在1947年，贝尔电话实验室发明了电子晶体管，部分归功于对半导体组件和PN结的进一步理解。
红外线LED是在1962年使用由砷化镓材料做成的PN结而创造出来的。上世纪60年代末，红色和绿色的LED在不同的国家运用由磷化镓材料做成的PN结制造而成。然而蓝光LED的发展则一直是科学家们的难题。
最初，人们尝试用硒化锌和碳化硅来做发蓝光的二极管，但无法实现高效能的发光。促使蓝光LED的研发得以向前发展的材料是氮化镓。
在1974年，赤崎勇开始研究氮化镓，并且接受了名古屋大学的教授职位，与天野浩并肩继续其研究。到了1986年，金属有机物气相外延技术被应用来制造具有高晶体质量和优质光学性能的氮化镓。之后中村修二研发出一种类似的方法以实现低温环境下生成氮化镓。
在上世纪90年代初期，由赤崎和中村分别领导的研究组所取得的半导体异质结构研究成果是蓝光LED研究发展历程中的关键一步。1994年，中村使用双异质结氮化铟镓/氮化铝镓来制造一种具有2.7%量子效率的装置，继而为轻易制造出高效能蓝光LED打开了大门。
照明技术如今正在经历着一场重大的变革，电灯泡和荧光灯正逐渐被LED所取代。当前白光LED在电转光上能达到50%左右的能效。1879年，由托马斯·爱迪生发明的传统电灯泡仅具有4%的能效，两者相比，白光LED实在是巨大的进步。
白光LED的寿命约有十万小时，且其价格很快会因为市场需求的增长而愈趋合理。以LED取代传统的电灯泡将会大幅度降低因为照明所带来的对于地球的能源需求，目前全球电力消费的20%至30%都用于照明。
目前，LED技术用于众多手机、笔记本电脑和电视屏幕的背光屏幕中。蓝光氮化镓二极管激光器被应用于蓝光光盘的数据存储支撑技术上，人们预测蓝光光盘会取代DVD光盘。
将来会有一天，人们还会在水净化技术中看到氮化铟镓/氮化铝镓LED的应用，因为它们的紫外线能够破坏病毒和细菌的DNA。而对于那些电力设施比较落后的国家，人们相信太阳能驱动的白光LED将会替代煤油灯来照亮夜晚。