利用InAs/GaAs数字合金超晶格改进InAs量子点有源区的结构设计

Improving structure design of active region of InAs quantum dots by using InAs/GaAs digital alloy superlattice

利用分子束外延技术,通过InAs/GaAs数字合金超晶格代替传统的直接生长InGaAs层的方式,在GaAs(100)衬底上生长了InAs量子点结构并成功制备了1.3μm InAs量子点激光器.通过原子力显微镜和光致荧光谱测试手段,对传统生长模式和数字合金超晶格生长模式的两种样品进行了表征,研究发现采用32周期InAs/GaAs数字合金超晶格样品的量子点密度非常高,发光性能良好.通过与常规生长方式所制备激光器的性能对比,发现采用InAs/GaAs数字合金超晶格生长InAs量子点的有源区也可以得到高质量的激光器.利用该方式生长的InAs量子点激光器的阈值电流为24 mA,相应的阈值电流密度仅为75 A/cm^(2),最高工作温度达到120℃.InAs/GaAs数字合金超晶格既可以保证生长过程中源炉的温度保持不变,还可以对InGaAs层的组分实现灵活调控.不需要改变生长速度,通过改变InAs/GaAs数字合金超晶格的周期数以及InAs层和GaAs层的厚度,便可以获得任意组分的InGaAs,从而得到不同发光波长的激光器.这种生长方式对量子点有源区的结构设计和外延生长提供了新思路.

A 1.3-μm InAs quantum dot laser has been successfully fabricated on a GaAs(100)substrate by molecular beam epitaxy(MBE)technique through using InAs/GaAs digital alloy superlattices instead of the conventional InGaAs layer.The samples grown by conventional growth method and the digital alloy superlattice growth method are characterized by atomic force microscope(AFM)and photoluminescence(PL)spectroscopy.It is found that 8-period sample possesses a low quantum dot density and poor luminescence performance.With the increase of the number of growth periods,the quantum dot density of the sample increases and the luminous performance improves.This indicates that the quality of the grown sample improves with the increase of InAs/GaAs period of the InGaAs layer.When the total InAs/GaAs period is 32,the quantum dot density of the sample is high and the luminescence performance is good.After the experimental measurement,the sample DAL-0 fabricated by conventional growth method and the sample DAL-32(32-periods InAs/GaAs digital alloy superlattices)are utilized to fabricate quantum dot laser by standard process.The performances of two types of quantum dot lasers obtained with different growth methods are characterized.It is found that the InAs quantum dot lasers fabricated by the sample grown by digital alloy superlattice method have good performances.Under continuous wave operation mode,the threshold current is 24 mA corresponding to a threshold current density of 75 A/cm2.The highest operation-temperature reaches 120℃.In addition,InAs quantum dot laser using digital alloy superlattice has good temperature stability.Its characteristic temperature is 55.4 K.Compared with the traditional laser,the InAs quantum dot laser grown by InAs/GaAs digital alloy superlattice has good performance in terms of threshold current density,output power and temperature stability,which indicates that high-quality laser can be obtained by this growth method.Using the InAs/GaAs digital alloy superlattice growth method,the InGaAs composition can be changed without changing the temperature of the source oven.Thus InAs quantum dot lasers with different luminescence wavelengths can be obtained through this growth method.The InAs/GaAs digital alloy superlattice structure can be used to realize different averaging of In content in the growth structure.The method provides a new idea for designing and growing the active region of quantum dot laser.