蓝光-宽带隙激光器.ppt

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1、Wide BandgapSemiconductor-Based Lasers,王伟平 2014-1-9,Part 1：GaN blue laser diodes,彩色激光显示 打印和扫描：快速、高分辨率 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 Application,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 光学元部件及光盘片材料的光学透过率等限制,1-2 Optical Storage,400-430 nm,1982年 AlGaAs/GaAs(780nm)异质结

2、激光器作为光源的CD播放机,1985年，Kabayashi InGaAlP(670nm)红光 激光器的室温连续激射,1992年，Hiroyama InGaAlP(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10000h,1-3 Difficulties and Breakthroughs,难点 缺乏晶格常数匹配、热胀系数接近的热稳定的衬底材料 p型GaN外延层难以获得 突破 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

3、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外延层,1991 年首次获得GaN外延层室温光泵浦下的受激发射。 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。 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。,1-4 Growth,衬底的选择,生长技术 双流生长技术 外延侧向过生长 悬挂式外延,F-P腔结构InGaN基激光器 电注入的三级

4、Bragg光栅紫光DFB激光器,1-5 Cavity structure,垂直腔面发射激光器 极化声子激光器,Part 2：GaN-Based VCSEL and GaN-/ZnO-Based Polariton Lasers,2-1 Introduction,microcavity (MC)-based VCSEL polariton lasers,With edge-emitting GaN-based lasers in commercial systems, attention is shifting to more demanding and rewarding emitters.,

5、High-speed, high-resolution laser printing and scanning New types of coherent optical but nearly thresholdless sources,Observation of spontaneous em-ission buildup in polariton lasing emission is attributed to a Bose Einstein condensate of cavity pol-aritons.,2-2 GaN-BASED VCSEL,The beam of a VCSEL

6、is characterized by a lower divergence angle compared with that of the edge-emitting lasers, making them favored for use in fiber-optic communications. Gain region is very short in vertical cavity devices as compared the edge-emitter varieties, the required reflectivities of the top and bottom DBRs

7、must be well above 90% in order to overcome optical losses for lasing.,VCSELs emit perpendicular to the active region surface, allowing their fabrication in a dense two-dimensional array.,2-2-1 Optically Pumped GaN-Based VCSEL(1),A significant narrowing of the emission spectra from 2.5 nm to 0.1 nm

8、above the threshold was observed, which is direct evidence of lasing os-illation in the 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 emi

9、ssion spectra from 0.8 nm below threshold to less than 0.1 nm above threshold.,Bottom DBR: 43-pair GaN/Al0.34Ga0.66N Cavity: 26 sets of In0.01Ga0.99N/In0.1Ga0.9N MQWs Top DBR:15-pair ZrO2/SiO2,2-2-1 Optically Pumped GaN-Based VCSEL(2),Top/Bottom DBR: SiO2/HfO2 Cavity: InGaN/GaN/AlGaN QW heterostruct

10、ure,Demonstrated a cavity Q factor exceeding 600 in initial experiments, suggesting that the approach can be useful for blue and near ultraviolet RCLED and VCSEL.,Bottom DBR: 60-pair GaN/Al0.25Ga0.75N Cavity: 20 sets of In0.03Ga0.97N/InGaN MQWs Top DBR:15-pair SiO2/HfO2,Demonstrated quasi-continuous

11、-wave (CW) lasing operation at room temperature using a hybrid cavity structure,2-2-1 Optically 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 Al

12、InN/GaN material system to realise high quality MOVPE-grown advanced optoelectronic devices such as VCSELs on GaN quasi-substrates.,Top/Bottom DBR: SiO2/ZrO2 Cavity: three periods of In0.02Ga0.98N(5nm)/In0.15Ga0.85N(2.5nm) QWs sandwiched between Al0.07Ga0.93N layers,Bottom DBR: 28-pair AlInN/GaN Cav

13、ity: 2 sets of In0.15Ga0.85N/GaN MQW Top DBR:23-pair AlInN/GaN DBR,Crack-free high reflectivity DBRs,2-2-1 Optically Pumped GaN-Based VCSEL(4),A low average threshold pump energy density of 200 J/cm2 was achieved in a crack-free planar hybrid. This is also conducive for electrical injection.,Demonst

14、rated an efficient current injection scheme in micron-scaled areas for high current density operation in vertical light emitting devices by using a LM AlInN oxidized layer. A current density of the order of 20 kA/cm2 has been achieved, a value which should fulfill the injection requirements for nitr

15、ide-based VCSELs.,Bottom DBR: 39.5-pair Al0.82In0.18N/GaN Cavity: 3 sets of In0.14Ga0.86N/GaN QWs Top DBR:13-pair SiO2/Si3N4,2-2-2 Electrically Pumped GaN-Based VCSEL(1),电泵浦的GaN基VCSEL难点 (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。 (

16、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, 更增大了电极材料的难度。 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。,2-2-2 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 f

17、our pairs of AlN/GaN Cavity: n-GaN(790nm) ten periods of In0.2Ga0.8N(2.5nm)/GaN(7.5 nm) MQWs p-GaN(120nm) Top DBR:8-pair Ta2O5/SiO2 DBR,2-2-2 Electrically Pumped GaN-Based VCSEL(3),Bottom DBR: 7-pair SiO2/Nb2O5 Cavity: n-GaN(790nm) 2-pair of InGaN (9nm)/GaN (13nm) MQWs p-GaN(120nm) Top DBR:11.5-pair

18、 SiO2/Nb2O5,Fabricated a vertical-current-injection GaN-based VCSEL Lasing action at RT was realized under CW current operation.,2-3 Wide Bandgap Semiconductor Polariton Devices,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。,Polariton,BoseEinstein condensatio

19、n,Lasing Condition,Polariton Lasers,Extremely low threshold lasers,1998年，Le Si Dang与其合作者在液氦温度下观察到极化激光。 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。,2-3-1 GaN-Based Microcavities-Polariton Lasers,A realistic model for a room temperature polariton laser has

20、 been proposed for a GaN MC . It shows an extremely low threshold power at room temperature and a high quantum efficiency.,Bottom DBR: 11-pair Al0.2Ga0.8N/Al0.9Ga0.1N Cavity: 9 GaN QWs four monolayers Top DBR:14-pair Al0.2Ga0.8N/Al0.9Ga0.1N,Bottom DBR: 34-pair Al0.85In0.15N/Al0.2Ga0:8N Cavity: bulk

21、GaN Top DBR:10-pair SiO2/Si3N4,Observe a room-temperature low-threshold transition to a coherent polariton 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 VCSELs,2-3-2

22、 ZnO-Based Microcavities(1),Another wide-bandgap semiconductor, ZnO, is an attractive candidate for UV 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/GaN Cavity: bulk ZnO Top DBR:8-pair SiO2/Si3N4,Rabi

23、 splitting,A large vacuum Rabi splitting of 50 meV at RT was obtained,which is larger than that observed in bulk GaN-based MCs. Results indicate that ZnO-based microcavities can be used to realize polariton lasers.,2-3-2 ZnO-Based Microcavities(2),Bottom DBR: a 30-pair AlN/Al0.23Ga0.77N Cavity: bulk

24、 ZnO Top DBR:9-pair SiO2/HfO2,The strong exciton-photon coupling at RT has been observed from the ZnO-based hybrid microcavity structure. Large vacuum Rabi splitting value: about 58 meV,3. CONCLUSION,Introduce wide bandgap semiconductor laser, including applications, especially in Optical Storage, d

25、ifficulties and breakthroughs, growth techniques and cavity structures.,Reviewed the recent progress in wide-bandgap semiconductor-based surface-emitting laser structures such as GaN-based VCSELs and GaN-/ZnO-based polariton lasers.,References,The blue laser diode 半导体蓝光激光器 Wide Bandgap Semiconductor

26、-Based Surface-Emitting Lasers Lasing emission from an InGaN VCSEL 宽禁带 GaN 基半导体激光器进展 GaN基蓝光半导体激光器的发展 蓝光激光器的应用与发展 A vertical cavity light emitting InGaN quantum well heterostructure Near ultraviolet optically pumped vertical cavity laser 低维半身傩结构材料及其器件应用研究迹展 为什么我们需要极化声子激光器? 电注入连续波蓝光GaN基 Cavity polarit

27、ons in ZnO-based hybrid microcavities Room-TemperaturePolariton Lasing in Semiconductor Microcavities 垂直腔面发射激光器 半导体泵浦全固体蓝光激光器的研究进展 Low-threshold lasing of InGaN vertical-cavity surface-emitting lasers with dielectricdistributed Bragg reflectors Blue lasing at room temperature in an optically pumped

28、lattice-matched AlInN/GaN VCSEL structure Efficient current injection scheme for nitride vertical cavity surface emitting lasers CW lasing of current injection blue GaN-based vertical cavity surface emitting laser Room-Temperature CW Lasing of a GaN-Based Vertical-Cavity Surface-Emitting Laser by Cu

29、rrent Injection Lattice-matched distributed Bragg reflectors for nitride-based vertical cavity surface emitting lasers ZnODevicesandApplications: A Review of Current Status and Future Prospects Vacuum Rabi Splitting and its math methods/真空拉比分裂及其数学方法 Large vacuum Rabi splitting in ZnO-based hybrid microcavities observed at room temperature Comparison of strong coupling regimes in bulk GaAs, GaN, and ZnO semiconductor microcavities 。,Thanks！,