|Abstract: ||在本論文中，吾人研製以II-VI族硒化鋅及硫化鋅化合物半導體材料為基礎的異質接面短波長光偵測元件，包含具銦錫氧化物透明導電電極之金半金光二極體以及整合磷化銦鎵/砷化鎵異質接面電晶體和金半金光二極體之積體化光偵測器。在金半金光二極體的研究中，吾人以紅外線爐化學氣相沈積系統成長之硒化鋅/砷化鎵及硫化鋅/砷化鎵異質磊晶薄膜為光吸收材料，配合高透明度和導電度之銦錫氧化薄膜製成高波長鑑別率之金半金光二極體。在積體化光偵測器的研究中，吾人以新提出之氧化層遮罩磊晶技術於磷化銦鎵/砷化鎵異質接面電晶體磊晶片上製作硒化鋅/砷化鎵及硫化鋅/砷化鎵金半金光二極體，成功整合成具有信號放大功能的積體化光偵測器。 首先，吾人以紅外線爐化學氣相沈積系統成長硒化鋅/砷化鎵及硫化鋅/砷化鎵異質磊晶薄膜，並利用各種分析技術包括掃描式電子顯微鏡(SEM)、X射線繞射分析儀(XRD)、二次離子質譜儀(SIMS)、光致螢光掃描系統(PL)和霍爾量測系統(Hall measurement)分別對硒化鋅及硫化鋅磊晶薄膜分別進行結構、材料、光學和電性分析，實驗顯示以紅外線爐化學氣相沈積系統成長之硒化鋅/砷化鎵及硫化鋅/砷化鎵磊晶薄膜具有良好品質。 其次，最佳化參數製備之硒化鋅及硫化鋅異質磊晶薄膜則應用於具銦錫氧化物透明導電電極之金半金光二極體之製作，為獲得高光靈敏度之短波長光偵測元件，吾人亦進行銦錫氧化物薄膜的結構、材料、光學和電性分析，實驗顯示銦錫氧化物薄膜的品質於氮氣氣氛下經攝氏300度退火處理後獲得大幅度改善，電阻率及可見光頻譜範圍之光穿透率分別由1.38 × 10-1 Ω•cm和87.1 %改善至3.10 × 10-3 Ω•cm和88.9 %。最佳製程參數之銦錫氧化物薄膜則用以硒化鋅/砷化鎵及硫化鋅/砷化鎵金半金光二極體之製作，經由元件暗電流分析，銦錫氧化物/硒化鋅及銦錫氧化物/硫化鋅之蕭基位障分別為0.906 eV和1.031 eV。在5V偏壓下硒化鋅/砷化鎵及硫化鋅/砷化鎵金半金光二極體之最大光響應度分別為0.08 A/W和0.028 A/W，兩種感光元件皆具有超過103之波長鑑別率。此外亦對硒化鋅/砷化鎵金半金光二極體在不同偏壓下其光響應度對入射光波長的相依性進行研究，主要為探討磊晶層及基板內空乏區擴張造成之電流貫穿效應對元件光響應的影響。實驗顯示吾人製作硒化鋅/砷化鎵及硫化鋅/砷化鎵金半金光二極體具有理想之光靈敏度。 最後，吾人利用氧化層遮罩磊晶技術分別將硒化鋅/砷化鎵及硫化鋅/砷化鎵金半金光二極體與磷化銦鎵/砷化鎵異質接面電晶體晶片整合於砷化鎵晶片上，並製成硒化鋅及硫化鋅積體化短波長光偵測器。整合元件中以磷化銦鎵/砷化鎵異質接面電晶體為主的共射極組態電路可放大金半金光二極體產生之光電流。在波長為440nm及320nm的10μW功率光照射下，硒化鋅及硫化鋅積體化短波長光偵測器的電壓光響應度和電流放大率分別為-29.6 mV/μW和20.8及-8.7mV/μW和18.2。最大可測光功率則分別為94 μW及273 μW。實驗結果顯示本論文設計製作之硒化鋅及硫化鋅積體化短波長光偵測器極適合用於短波長光之偵測。此外，本論文發展之氧化層磊晶遮罩技術相信對II-VI化合物異質接面短波長光電積體元件發展上亦有助益。|
In this dissertation, the short-wavelength photodetectors based on II-VI ZnSe and ZnS compound semiconductors are investigated. The ZnSe and ZnS epilayers grown on GaAs substrate by means of the IR furnace chemical vapor deposition (CVD) were used to fabricate metal- semiconductor-metal (MSM) photodiodes as well as monolithically integrated photodetectors. First, according to the results from various analytic methods including the scanning electron microscope (SEM), x-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), photoluminescence spectroscopy (PL), and Hall measurements, the structural, optical, and electrical properties of the ZnSe and ZnS epilayers can be determined and then the proper growth conditions were obtained. The SEM morphologies of the epilayers can be used to estimate the growth rate. From the XRD, the strong peaks with a narrow FWHM of the oriented-(400) of as-grown ZnSe and ZnS were obtained which indicates the single crystalline structures. The SIMS depth profiles confirm the compositional uniformity of the epilayers. In PL measurement, the strong neutral near-band-edge (NBE) excitation emissions for the ZnS and the ZnSe epilayers were observed at 327 and 453 nm, respectively. These experimental results indicate the good optical quality and crystalline structure of the ZnSe and the ZnS epilayers grown on GaAs substrates utilizing the IR furnace CVD system. These ZnSe and ZnS epilayers were used to fabricate short-wavelength MSM photodetectors. Second, indium tin oxide (ITO) film was applied as the transparent electrodes of MSM photodetectors. For the purpose of improving the properties including transmittance and conductance, ITO films must suffer post-annealed treatment. The structural, optical, and electrical properties of ITO thin films deposited from an rf magnetron sputtering system were estimated by the SEM, XRD, AFM, and four point probe system. The chosen post-annealed condition is 300 °C in N2 for 1 hr. Subsequently, the ZnSe and ZnS MSM photodiodes with ITO electrodes were fabricated. The approximate Schottky barrier heights estimated from dark currents were 0.906 eV for the ITO/ZnSe and 1.031 eV for ITO/ZnS. The maximum photoresponsivity of 0.08 and 0.028 A/W, respectively for the ZnSe and ZnS MSM-PD were obtained. The MSM photodiodes based on these epilayers have shown high rejection ratio, which indicates the good quality of the epilayers. The dependence of the I-V characteristics and spectral photoresponse for the ZnSe MSM photodiode on the applied bias voltage was demonstrated. The result should help to better understand the physical behavior of the heterostructure. Third, a new type of monolithic integrated photodetector composed of an InGaP/GaAs heterojunction bipolar transistor (HBT) and a MSM photodiode was presented. The dc optical and electrical properties of the integrated photodetectors based on the ZnS or ZnSe epilayers have been demonstrated. The photocurrent of the MSM photodiode was enhanced successfully by a preamplifier circuit based on an InGaP/GaAs designed in the integrated photodetector. The current amplification ratios estimated at input optical power intensity of 10 μW were 20.8 for the ZnSe-based integrated photodetector and 18.2 for the ZnS-based integrated photodetector. The voltage amplification sensitivities of -29.6 and -8.7 mV/μW for the ZnSe-based and the ZnS-based integrated photodetectors were obtained. The maximal measurable input optical power intensities were 94 μW and 273 μW, respectively. These results indicate the usefulness of the patterned-oxide growth technique for the future development of the II-VI compounds -based short-wavelength optoelectronic integrated circuits (OEICs) applications.