宽沟道SI-GaAs衬底上适于光发射机的BH激光器

目前,光发射机中的激光器有采用MOCVD和MBE方法生长的多量子阱激光器,用LPE法生长的BH激光器。我们根据现有的实验条件,为了制作单片集成的光发射机,在沟道SI-GaAs衬底上采用两次液相外延生长BH激光器,实现了表面平面化。在800℃一次外延生长四层。第一层n⁺-GaAs缓冲层,第二层N-GaAlAs下限制层,第三层非掺杂构GaAs有源层,第四层为P-GaAlAs上限制层。采用适当的腐蚀条件刻蚀出有源区最窄的燕尾形隐埋条。在二次外延中,我们仅装一槽GaAlAs源液,在晶片上仅停留一次便生长出两个掩埋层,且层间界面与有源区自对准。上层为N-GaAlAs,载流子浓度为10¹⁶cm^-3,下层为高阻伴随生长层。由于高阻伴随层的存在对电流产生了有有效的侧向限制作用,因此避免了通常的SiO₂膜沉积等一系列工艺,提高了成品率,减化了工艺程序。利用n型掩埋层和隐埋条区P型上限制层之间铝组分及载流子类型、浓度的差异,虽然做一种宽接触电极,但由于隐埋条区上有良好的欧姆接触,而在掩埋层上为非良欧姆接触,所以起到了一定的电流外限制作用。n型电极是从n⁺-GaAs层引出的。 这种沟道SI-GaAs衬底正装GaAlAs/GaAs BH激光器室温连续工作阈值电流为55mA,P-I曲线在100℃仍有良好的线性关系。

A BURIED-HETEROSTRUCTURE GaAIAs LASER ON A GROOVE SEMI-INSULATION SUBSTRATE FOR A MONOLITHIC INTEGRATED TRANSMITTER

Optoelectronic integrated circuit (OEIC) in which both photonic and electronic devices are monolithically integrated on a single chip can exhibit various advantages in improving performance, functionality, reliability and less cost. Owing to their low threshold current and high speed modulation characteristics, MQW-lasers and BH-lasers are used in OEIC. A buried-heterostructure(BH) GaAlAs laser is grown on a groove SI-GaAs substrate for a monolithic realized The use of SI-substrate is to reduce parasitic reactances and realize electronic isolatioa The fabrication process involves two-step LPE growth. First, an etched groove was formed along the (110)-direction on the (001) substrate. Secondly, four layers of n⁺-GaAs (8μm-thick, Te-doped to 1× 10¹⁹cm^-3), N-Ga0.75 Al0.25 As (0.8μm-thick, Sn-doped to 2× 10¹⁷cm-8), GaAs (0.2μm-thick, undoped), P-Ga0.75 Al0.25 As (1μm-thick, Ge-doped to 2 × 10¹⁷ cm^-3) were grown in the first step growth. Buried mesa stripes were etched down to n⁺-GaAs layer (stripe width 6-8μm) along (110) direction. In the second-step growth, two burying layers were grown by a undoped GaAlAs growth solution contacting with the surface of wafer only once. The first layer is high resistance layer. The second is N-Ga0.6 Al0.4 As (3× 10¹⁶cm^-3). The interface between the first and second layers is adgacent to the active layer. The high resistance layer confinec success-fully the current Au-Zn/Au was evaporated on whole wafer to form P-contact. A positive-acting photoresist (212) is coated in spinning and patterned. After etching the useless layer down ro n⁺-GaAs buffer layer, and using a lift-off technique, the n-con-tact is formed by evaporation of Au-GeNi, followed by alloying. The laser is mounted with junction up on a copper heat sink.The CW threshold current of the BH laser on a groove SI-substrate is 50mA at room temperature. A stable transverse mode operation and linear light/ current charac-teristics were achieved. In the recent, 20mA threshold current were realized.