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1、Wide BandgapSemiconductor-Based Lasers王伟平王伟平2014-1-92014-1-901v彩色激光显示v打印和扫描：快速、高分辨率v存储：CD(780 nm)AlGaAs基激光器 VCD(635 nm或650 nm)AlGaInP激光器 DVD(410nm) InGaN 激光器1-1 Application2v提高物镜的数值孔径NA值 容量与光源波长的2次方成反比 v光学元部件及光盘片材料的光学透过率等限制1-2 Optical Storage400-430 nm1982年AlGaAs/GaAs(780nm)异质结激光器作为光源的CD播放机1985年，Kab
2、ayashiInGaAlP(670nm)红光激光器的室温连续激射1992年，HiroyamaInGaAlP(630nm)红光半导体激光器1996年，日亚和中村GaN(400nm)蓝紫光半导体激光器1999年，日亚实现商品化GaN(400nm)蓝光半导体激光器寿命10000h31-3 Difficulties and Breakthroughs难点难点v缺乏晶格常数匹配、热胀系数接近的热稳定的衬底材料vp型GaN外延层难以获得突破突破v高质量GaN外延层的生长 1986年Amano利用低温生长的AlN或GaN过渡层或成核层,得到表面平坦如镜低剩余载流子浓度、高电子迁移率和高荧光效率的高质量GaN
3、外延层,1991 年首次获得GaN外延层室温光泵浦下的受激发射。v低阻p-GaN 的获得 1989年Amano等人利用低能电子辐照实现了Mg掺杂低阻p型GaN。1991年Nakamura等人在700以上无氢的氮气氛中退火 ,也获得了低阻p-GaN。v高质量InGaN外延层的生长 有源层内由 In 组分涨落引起的深局域化能态是发光二极管高效发光的关键 ,只有掺有In的GaN有源层才可能得到室温带间跃迁。41-4 Growthv衬底的选择v生长技术1.双流生长技术2.外延侧向过生长3.悬挂式外延5vF-P腔结构InGaN基激光器v电注入的三级Bragg光栅紫光DFB激光器1-5 Cavity st
4、ructurev垂直腔面发射激光器v极化声子激光器672-1 Introductionvmicrocavity (MC)-based VCSELvpolariton lasersWith edge-emitting GaN-based lasers in commercial systems, attention is shifting to more demanding and rewarding emitters. lHigh-speed, high-resolution laser printing and scanninglNew types of coherent optical b
5、ut nearly thresholdless sourceslObservation of spontaneous em-ission buildup in polariton lasing emission is attributed to a Bose Einstein condensate of cavity pol-aritons. 82-2 GaN-BASED VCSELvThe beam of a VCSEL is characterized by a lower divergence angle compared with that of the edge-emitting l
6、asers, making them favored for use in fiber-optic communications.vGain region is very short in vertical cavity devices as compared the edge-emitter varieties, the required reflectivities of the top and bottom DBRs must be well above 90% in order to overcome optical losses for lasing.VCSELs emit perp
7、endicular to the active region surface, allowing their fabrication in a dense two-dimensional array. 92-2-1 Optically Pumped GaN-Based VCSEL(1)A significant narrowing of the emission spectra from 2.5 nm to 0.1 nm above the threshold was observed, which is direct evidence of lasing os-illation in the
8、 In0.1Ga0.9N VCSEL.Science 17 September 1999: Vol. 285 no. 5435 pp. 1905-1906 Lasing action was observed at a wavelength of 399 nm under optical excitation and confirmed by a narrowing of the linewidth in the emission spectra from 0.8 nm below threshold to less than 0.1 nm above threshold.Bottom DBR
9、: 43-pair GaN/Al0.34Ga0.66NCavity: 26 sets of In0.01Ga0.99N/In0.1Ga0.9N MQWsTop DBR:15-pair ZrO2/SiO2102-2-1 Optically Pumped GaN-Based VCSEL(2)Top/Bottom DBR: SiO2/HfO2Cavity: InGaN/GaN/AlGaN QW heterostructureDemonstrated a cavity Q factor exceeding 600 in initial experiments, suggesting that the
10、approach can be useful for blue and near ultraviolet RCLED and VCSEL.Bottom DBR: 60-pair GaN/Al0.25Ga0.75NCavity: 20 sets of In0.03Ga0.97N/InGaN MQWsTop DBR:15-pair SiO2/HfO2Demonstrated quasi-continuous-wave (CW) lasing operation at room temperature using a hybrid cavity structure112-2-1 Optically
11、Pumped GaN-Based VCSEL(3)Exhibited a high Q factor of 460, a spontaneous emission factor of about 10-2, and low threshold of 5.1mJ/cm-2.Demonstrated the great potential offered by the lattice-matched AlInN/GaN material system to realise high quality MOVPE-grown advanced optoelectronic devices such a
12、s VCSELs on GaN quasi-substrates. Top/Bottom DBR: SiO2/ZrO2Cavity: three periods of In0.02Ga0.98N(5nm)/In0.15Ga0.85N(2.5nm) QWs sandwiched between Al0.07Ga0.93N layersBottom DBR: 28-pair AlInN/GaNCavity: 2 sets of In0.15Ga0.85N/GaN MQWTop DBR:23-pair AlInN/GaN DBRCrack-free high reflectivity DBRs122
13、-2-1 Optically Pumped GaN-Based VCSEL(4)lA low average threshold pump energy density of 200 J/cm2 was achieved in a crack-free planar hybrid.lThis is also conducive for electrical injection.lDemonstrated an efficient current injection scheme in micron-scaled areas for high current density operation
14、in vertical light emitting devices by using a LM AlInN oxidized layer.lA current density of the order of 20 kA/cm2 has been achieved, a value which should fulfill the injection requirements for nitride-based VCSELs.Bottom DBR: 39.5-pair Al0.82In0.18N/GaNCavity: 3 sets of In0.14Ga0.86N/GaN QWsTop DBR
15、:13-pair SiO2/Si3N4132-2-2 Electrically Pumped GaN-Based VCSEL(1)v电泵浦的电泵浦的GaNGaN基基VCSELVCSEL难点难点v(1)难以获得具有高质量和高反射率的DBR AlxGa1-xN和GaN之间折射率相差较大, 因此二者搭配而成的DBR为GaN基VCSEL所普遍采用。但AlxGa1-xN和GaN之间晶格失配严重, 它们的热膨胀系数也相差较大。v(2)缺少合适的p型接触电极材料 p型GaN的功函数很高, 很难找到理想的低阻欧姆接触电极材料。VCSEL的电流注入既要求低接触电阻又要求出光孔径具有非常低的光学损耗, 更增大了电
16、极材料的难度。v解决方案解决方案：在AlN/GaN DBR的制造过程中引入了超晶格结构, 在出光孔径上以氧化铟锡(ITO)作为接触电极。142-2-2 Electrically Pumped GaN-Based VCSEL(2)Bottom DBR: 29-pair AlN/GaN DBR three sets of a 5.5-pair of AlN/GaN superlattice was inserted every four pairs of AlN/GaN Cavity: n-GaN(790nm) ten periods of In0.2Ga0.8N(2.5nm)/GaN(7.5 n
17、m) MQWs p-GaN(120nm)Top DBR:8-pair Ta2O5/SiO2 DBR152-2-2 Electrically Pumped GaN-Based VCSEL(3)Bottom DBR: 7-pair SiO2/Nb2O5Cavity: n-GaN(790nm) 2-pair of InGaN (9nm)/GaN (13nm) MQWs p-GaN(120nm)Top DBR:11.5-pair SiO2/Nb2O5lFabricated a vertical-current-injection GaN-based VCSELlLasing action at RT
18、was realized under CW current operation. 162-3 Wide Bandgap Semiconductor Polariton Devicesv在1996年Imamoglu及其合作者提出了极化声子激光器的概念,他们是基于一种叫激子极化声子的准粒子提出此概念，这种准粒子由光和物质组成，产生于适当设计的半导体晶体结构中。PolaritonBoseEinstein condensationLasing ConditionPolariton LasersExtremely lowthreshold lasers1998年，Le Si Dang与其合作者在液氦温度
19、下观察到极化激光。2007年，Southampton和Lausanne团队实现了具有光泵的第一个室温极化声子激光器。2012年，Iorsh基于氮化镓（GaN）微腔的电泵浦极化声子激光器优化方案。172-3-1 GaN-Based Microcavities-Polariton LasersA realistic model for a room temperature polariton laser has been proposed for a GaN MC .It shows an extremely low threshold power at room temperature and
20、a high quantum efficiency.Bottom DBR: 11-pair Al0.2Ga0.8N/Al0.9Ga0.1NCavity: 9 GaN QWs four monolayersTop DBR:14-pair Al0.2Ga0.8N/Al0.9Ga0.1NBottom DBR: 34-pair Al0.85In0.15N/Al0.2Ga0:8NCavity: bulk GaNTop DBR:10-pair SiO2/Si3N4Observe a room-temperature low-threshold transition to a coherent polari
21、ton state in bulk GaN microcavities in the strong-coupling regime.A clear emission threshold of 1 mW, 1 order of magnitude smaller than the best optically pumped (In,Ga)N quantum-well VCSELs182-3-2 ZnO-Based Microcavities(1)vAnother wide-bandgap semiconductor, ZnO, is an attractive candidate for UV
22、optoelectronics devices. ZnO has an exciton binding energy (60 meV) that is more than twice that of GaN (26 meV). Bottom DBR: 29-pair Al0.5Ga0.5N/GaNCavity: bulk ZnOTop DBR:8-pair SiO2/Si3N4Rabi splittingA large vacuum Rabi splitting of 50 meV at RT was obtained,which is larger than that observed in
23、 bulk GaN-based MCs.Results indicate that ZnO-based microcavities can be used to realize polariton lasers.192-3-2 ZnO-Based Microcavities(2)Bottom DBR: a 30-pair AlN/Al0.23Ga0.77NCavity: bulk ZnOTop DBR:9-pair SiO2/HfO2The strong exciton-photon coupling at RT has been observed from the ZnO-based hyb
24、rid microcavity structure. Large vacuum Rabi splitting value: about 58 meV203. CONCLUSIONIntroduce wide bandgap semiconductor laser, including applications, especially in Optical Storage, difficulties and breakthroughs, growth techniques and cavity structures.Reviewed the recent progress in wide-ban
25、dgapsemiconductor-based surface-emitting laser structuressuch as GaN-based VCSELs and GaN-/ZnO-based polariton lasers.21References1.The blue laser diode2.半导体蓝光激光器3.Wide Bandgap Semiconductor-Based Surface-Emitting Lasers4.Lasing emission from an InGaN VCSEL5.宽禁带 GaN 基半导体激光器进展6.GaN基蓝光半导体激光器的发展7.蓝光激光器
26、的应用与发展8.A vertical cavity light emitting InGaN quantum well heterostructure9.Near ultraviolet optically pumped vertical cavity laser 10.低维半身傩结构材料及其器件应用研究迹展11.为什么我们需要极化声子激光器? 12.电注入连续波蓝光GaN基13.Cavity polaritons in ZnO-based hybrid microcavities14.Room-TemperaturePolariton Lasing in Semiconductor Micr
27、ocavities15.垂直腔面发射激光器16.半导体泵浦全固体蓝光激光器的研究进展17.Low-threshold lasing of InGaN vertical-cavity surface-emitting lasers with dielectricdistributed Bragg reflectors18.Blue lasing at room temperature in an optically pumped lattice-matched AlInN/GaN VCSEL structure19.Efficient current injection scheme for n
28、itride vertical cavity surface emitting lasers20.CW lasing of current injection blue GaN-based vertical cavity surface emitting laser21.Room-Temperature CW Lasing of a GaN-Based Vertical-Cavity Surface-Emitting Laser by Current Injection22.Lattice-matched distributed Bragg reflectors for nitride-bas
29、ed vertical cavity surface emitting lasers23.ZnODevicesandApplications: A Review of Current Status and Future Prospects24.Vacuum Rabi Splitting and its math methods/真空拉比分裂及其数学方法25.Large vacuum Rabi splitting in ZnO-based hybrid microcavities observed at room temperature26.Comparison of strong coupling regimes in bulk GaAs, GaN, and ZnO semiconductor microcavities27.。22Thanks！23
