Characterizations of the Tm-doped InGaAs layers grown by liquid phase epitaxy.

• Main Authors: Hsueh Sheng-Yuan, 薛勝元
• Other Authors: Uen Wu-Yih
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/98767696662263850833

碩士 === 中原大學 === 電子工程研究所 === 86 === Recently, studies on the effects of doping rare-earth (RE) elements onIII-V compound semiconductors have attracted much attention since theseelements, such as Yb, Gd, and Er exhibit impurity gettering effect due totheir strong affinity to oxygen and other group VI elements. Particularly, itis indicated doping Er into the InGaAs layer can present a strong characteristicluminescence with the wavelength fixed at 1.54mm under any temperature variations. This has paved the way for a widespread application of the Er-doped semiconductors in optical communication systems. In this study, we investigate for the first time the influence of Tm doping on the In0.53Ga0.47As epilayers on (100)-oriented InP substrates by liquid-phase epitaxy (LPE). The crystal structure, and the related electrical and opticalproperties of the In0.53Ga0.47As epilayers are analyzed. It is found the surfacemorphologies of the In0.53Ga0.47As layers become poorer since the latticemismatch increases as the Tm weight percentage increases. Also, from the Hall measurements, unintentionally doped In0.53Ga0.47As layers show n-type conductivity with a background carrier concentration of 4.34*1016cm-3. Otherwise, all the Tm-doped samples grown on the same growth conditionsas the undoped one also demonstrate n-type conductivity, however, give a higher carrier concentration of the order of 1017cm-3. No reduction in the background carrier concentration has been achieved by Tm doping. This result helps us to conclude that Tm, unlike other reported RE elements that simply play a role in the impurity getting effect, but it also acts as a donor in the In0.53Ga0.47As layers. According to the analysis of SIMS, we can obtain a uniform distribution of Tm is observed along the thickness direction. This result can be explained by those Tm atoms not only interact strongly with the impurities of S, Si, C, O, etc., in the growth solution, but also are incorporated in the In0.53Ga0.47As epitaxial structure. Additionally, the photoluminescence measurements performed at 23K, we observed that the main peak of the Tm-doped sample is left-shifting 38nm from that of the undoped one. Also, the impurity concentration profile of the same sample obtained from electro-chemical C-V measurement. It indicates a high-level doping of Tm with the impurity concentration over 1018/cm3. Based on the results given above, it is possible to ascribe the left-shifting luminescence to the electron-hole pair recombination between a new donor level resulting from Tm doping, and the valence band. Finally, two PIN photodetectors fabricated on undoped and Tm-doped material structures, respectively, are compared to further study the influences of Tm doping. The dark current of the Tm-doped device with a planar area of6.16x10-4cm2 is 1.02nA while that of the undoped one is 24.6nA.