JP2013058566A - Photoelectric conversion element, photodetector, and solar cell - Google Patents

Photoelectric conversion element, photodetector, and solar cell Download PDF

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JP2013058566A
JP2013058566A JP2011195441A JP2011195441A JP2013058566A JP 2013058566 A JP2013058566 A JP 2013058566A JP 2011195441 A JP2011195441 A JP 2011195441A JP 2011195441 A JP2011195441 A JP 2011195441A JP 2013058566 A JP2013058566 A JP 2013058566A
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photoelectric conversion
layer
conversion element
geo
film
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Mitsuru Takenaka
充 竹中
Shinichi Takagi
信一 高木
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University of Tokyo NUC
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element, a photodetector, and a solar cell, capable of improving device performance more than those of conventional types.SOLUTION: By forming a GeOfilm 10 on a surface of a photoelectric conversion layer 5 composed of Ge and making interface level density between the photoelectric conversion layer 5 and the GeOfilm 10 no more than 10[eVcm], it is possible to reduce a dark current of the photoelectric conversion layer 5, suppress surface recombination, and improve performances of various devices using a photoelectric conversion function more than those of conventional types.

Description

本発明は、光電変換素子、光検出器及び太陽電池に関し、例えばGe（ゲルマニウム）からなる光電変換層を備えた光電変換素子に適用して好適なものである。   The present invention relates to a photoelectric conversion element, a photodetector, and a solar cell, and is suitable for application to a photoelectric conversion element including a photoelectric conversion layer made of, for example, Ge (germanium).

近年、Geを光電変換素子として用いたGeフォトディテクター（PhotoDetectors：PD、以下これを光検出器と呼ぶ）は、既存のSiCMOS（Complementary Metal Oxide Semiconductor）プラットフォームに整合可能であることから、活発に研究が進められている（例えば、非特許文献１参照）。例えば、光検出器に用いる光電変換素子としては、Siの基板上にp型のp-Ge層を備え、このp-Ge層の一部にイオン注入を行って、p-Ge層表面にn型のn-Ge層を形成したpn接合構造の光電変換素子が知られている。   In recent years, Ge photodetectors (PhotoDetectors: PD, hereinafter referred to as photodetectors) using Ge as a photoelectric conversion element can be matched to the existing SiCMOS (Complementary Metal Oxide Semiconductor) platform, and are actively researched. (For example, refer nonpatent literature 1). For example, as a photoelectric conversion element used for a photodetector, a p-type p-Ge layer is provided on a Si substrate, and ion implantation is performed on a part of the p-Ge layer, and n is formed on the surface of the p-Ge layer. A photoelectric conversion element having a pn junction structure in which a n-Ge layer of a type is formed is known.

このような光電変換素子では、SiとGeとの結晶格子不整合からくる格子欠陥や、イオン注入を用いた接合形成時の結晶欠陥による暗電流が大きいという問題が指摘されている。しかしながら、このような光電変換素子における暗電流については、製造過程において、Ge中へのAsの気相式ドーピングを行って高品質のn+/p接合を作ることで、イオン注入と比較して2桁ほど減らせることができる。   In such a photoelectric conversion element, a problem has been pointed out that a dark current is large due to a lattice defect caused by a crystal lattice mismatch between Si and Ge and a crystal defect at the time of forming a junction using ion implantation. However, the dark current in such a photoelectric conversion element is 2 in comparison with ion implantation by making a high-quality n + / p junction by performing vapor phase doping of As into Ge in the manufacturing process. It can be reduced by an order of magnitude.

J.Michel et al.,Nature photon.,Vol.4,pp.527-534,2010J. Michel et al., Nature photon., Vol. 4, pp. 527-534, 2010

ところが、このような光電変換素子では、他にも、p-Ge層及びn-Ge層の光電変換層表面において発生するリーク電流が、暗電流増大の大きな要因となっていることが分かった。特に、導波路型の光検出器に用いる光電変換素子では、体積に比較し光電変換層の表面積が大きくなることから、トラップ準位アシスト電流のような、表面のリーク電流を低減させることが特に重要になる。そして、このような光電変換素子では、暗電流を低減して、微弱光をも検出できるように光検出器の性能を向上させることも望まれる。   However, in such a photoelectric conversion element, it has been found that the leakage current generated on the photoelectric conversion layer surfaces of the p-Ge layer and the n-Ge layer is a major factor in increasing the dark current. In particular, in the photoelectric conversion element used for the waveguide type photodetector, the surface area of the photoelectric conversion layer is larger than the volume, and therefore it is particularly preferable to reduce the surface leakage current such as the trap level assist current. Become important. In such a photoelectric conversion element, it is also desired to improve the performance of the photodetector so that dark current can be reduced and even weak light can be detected.

ところで、このようなGeにて形成した光電変換素子は、太陽電池の技術分野にも用いられることも考えられているが、この場合、光電変換層表面において表面再結合が生じることで、光電変換層で発電電圧が損失してしまうという問題があった。そのため、このような太陽電池に用いられる光電変換素子でも、発電電圧の損失を低減して、太陽電池の性能を向上させることが望まれる。   By the way, the photoelectric conversion element formed of such Ge is also considered to be used in the technical field of solar cells. In this case, surface recombination occurs on the surface of the photoelectric conversion layer. There was a problem that the generated voltage was lost in the layer. Therefore, it is desired that even in the photoelectric conversion element used in such a solar cell, the loss of the generated voltage is reduced and the performance of the solar cell is improved.

本発明は以上の点を考慮してなされたもので、機器の性能を従来よりも向上し得る光電変換素子、光検出器及び太陽電池を提案することを目的とする。   The present invention has been made in consideration of the above points, and an object of the present invention is to propose a photoelectric conversion element, a photodetector, and a solar cell that can improve the performance of the device as compared with the conventional one.

かかる課題を解決するため本発明の請求項１の光電変換素子は、Geを含む光電変換層と、前記光電変換層の表面に形成されたGeO2膜とを備え、前記光電変換層及び前記GeO2膜間の界面準位密度が1012[eV-1cm-2]以下であることを特徴とする。 In order to solve this problem, a photoelectric conversion element according to claim 1 of the present invention includes a photoelectric conversion layer containing Ge, and a GeO 2 film formed on a surface of the photoelectric conversion layer, and the photoelectric conversion layer and the GeO The interface state density between the two films is 10 12 [eV −1 cm −2 ] or less.

また、本発明の請求項５の光検出器は、請求項１〜４のうちいずれか１項記載の光電変換素子と、前記光電変換素子が光を受光することにより該光電変換素子から出力される出力信号を検知する出力検知手段とを備えたことを特徴とする。   Moreover, the photodetector of Claim 5 of this invention is output from this photoelectric conversion element when the photoelectric conversion element of any one of Claims 1-4 and the said photoelectric conversion element receive light. Output detecting means for detecting the output signal.

また、本発明の請求項６の太陽電池は、光電変換素子が光を受光することにより該光電変換素子にて電気エネルギーを生成する太陽電池であって、前記光電変換素子が請求項１〜４のうちいずれか１項記載の光電変換素子であることを特徴とする。   Moreover, the solar cell of Claim 6 of this invention is a solar cell which produces | generates an electrical energy in this photoelectric conversion element when a photoelectric conversion element receives light, Comprising: The said photoelectric conversion element is Claims 1-4. It is a photoelectric conversion element of any one of these, It is characterized by the above-mentioned.

本発明の請求項１によれば、光電変換層の表面にGeO2膜を形成し、光電変換層の表面及びGeO2膜間の界面準位密度を1012[eV-1cm-2]以下とすることで、暗電流を低減させたり、或いは、表面再結合を抑制し得、光電変換機能を用いた各種機器の性能を従来よりも向上し得る。 According to claim 1 of the present invention, a GeO 2 film is formed on the surface of the photoelectric conversion layer, and an interface state density between the surface of the photoelectric conversion layer and the GeO 2 film is 10 12 [eV −1 cm −2 ] or less. Thus, dark current can be reduced, or surface recombination can be suppressed, and the performance of various devices using a photoelectric conversion function can be improved as compared with the related art.

本発明の請求項５によれば、表面リーク電流により発生する暗電流を従来よりも低減し得、その結果、光電変換層にて微弱光を検出できるようになり、光電変換機能を用いた光検出器の性能を従来よりも向上し得る。   According to claim 5 of the present invention, the dark current generated by the surface leakage current can be reduced as compared with the conventional case. As a result, the weak light can be detected by the photoelectric conversion layer, and the light using the photoelectric conversion function can be detected. The performance of the detector can be improved as compared with the prior art.

本発明の請求項６によれば、光電変換層の表面にてキャリアの表面再結合を抑制し得ることから、光電変換層の表面での発電電圧の損失を低減でき、これにより光電変換の高効率化を実現し得、光電変換機能を用いた太陽電池の性能を従来よりも向上し得る。   According to the sixth aspect of the present invention, since the surface recombination of carriers can be suppressed at the surface of the photoelectric conversion layer, the loss of power generation voltage at the surface of the photoelectric conversion layer can be reduced. Efficiency can be realized and the performance of the solar cell using the photoelectric conversion function can be improved as compared with the conventional case.

本発明の第１の実施の形態による光検出器の断面構成を示す概略図である。It is the schematic which shows the cross-sectional structure of the photodetector by the 1st Embodiment of this invention. Ge層とGeO2膜との境界の側断面構成を示すTEM画像である。Is a TEM image showing a side sectional structure of a boundary between the Ge layer and the GeO 2 film. 界面準位密度とエネルギーとの関係を示すグラフである。It is a graph which shows the relationship between an interface state density and energy. 電流とバイアス電圧との関係を示すグラフである。It is a graph which shows the relationship between an electric current and a bias voltage. 暗電流と受光層底面の面積との関係を示すグラフである。It is a graph which shows the relationship between a dark current and the area of a light-receiving layer bottom face. 従来の光電変換素子の側断面構成を示す概略図である。It is the schematic which shows the side cross-section structure of the conventional photoelectric conversion element. 図６に示す従来の光電変換素子における電流とバイアス電圧との関係を示すグラフである。It is a graph which shows the relationship between the electric current and bias voltage in the conventional photoelectric conversion element shown in FIG. 第２の実施の形態による光検出器の断面構成を示す概略図である。It is the schematic which shows the cross-sectional structure of the photodetector by 2nd Embodiment. 第３の実施の形態による導波路型の光検出器の断面構成を示す概略図である。It is the schematic which shows the cross-sectional structure of the waveguide type photodetector by 3rd Embodiment. 第４の実施の形態による導波路型の光検出器の断面構成を示す概略図である。It is the schematic which shows the cross-sectional structure of the waveguide type photodetector by 4th Embodiment. 第５の実施の形態による導波路型の光検出器の断面構成を示す概略図である。It is the schematic which shows the cross-sectional structure of the waveguide type photodetector by 5th Embodiment. 第６の実施の形態による太陽電池の断面構成を示す概略図である。It is the schematic which shows the cross-sectional structure of the solar cell by 6th Embodiment.

以下図面に基づいて本発明の実施の形態を詳述する。
（１）第１の実施の形態
（１−１）光検出器の構成
図１において、１は本発明による光検出器を示し、上方からの光を受光することで電気信号を生成する垂直入射型の光電変換素子２と、光電変換素子２にて生成した電気信号を検知する出力検知手段３とから構成されている。実際上、光電変換素子２には、例えばp型のSiからなる基板４上に、pn接合構造を有したGeからなる光電変換層５が設けられている。光電変換層５は、極性がp型のp-Geからなるp-Ge層６と、p-Ge層６とは逆極性であるn型のn+-Ge（図１中、単に「n＋Ge」と表記する）からなるn＋Ge層７とから構成されており、p-Ge層６の表面上の一部に、パターニングされたn＋Ge層７が島状に形成されている。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(1) First Embodiment (1-1) Configuration of Photodetector In FIG. 1, reference numeral 1 denotes a photodetector according to the present invention, and a vertical incidence that generates an electric signal by receiving light from above. Type photoelectric conversion element 2 and output detection means 3 for detecting an electric signal generated by photoelectric conversion element 2. In practice, the photoelectric conversion element 2 is provided with a photoelectric conversion layer 5 made of Ge having a pn junction structure on a substrate 4 made of, for example, p-type Si. The photoelectric conversion layer 5 includes a p-Ge layer 6 made of p-Ge having a polarity of n, and an n-type n + -Ge having a polarity opposite to that of the p-Ge layer 6 (in FIG. 1, simply “n + Ge”). The patterned n + Ge layer 7 is formed in an island shape on a part of the surface of the p-Ge layer 6.

具体的にこの実施の形態の場合、光電変換層５は、p-Ge層６の表面と、n＋Ge層７の表面とが面一に形成され、このn＋Ge層７の表面一部にNiからなる電極９が形成されている。ここで、この光電変換層５は、上方から入射される光をp-Ge層６表面及びn＋Ge層７表面で受光し、受光した光によりn＋Ge層７の所定領域にて正孔及び電子（以下、これらを纏めて単にキャリアと呼ぶ）が生成され得る。光電変換層５は、このとき出力検知手段の印加手段によって逆バイアスが印加されることで、n＋Ge層７からp-Ge層６に流れる電気信号が生成され得る   Specifically, in the case of this embodiment, the photoelectric conversion layer 5 is formed such that the surface of the p-Ge layer 6 and the surface of the n + Ge layer 7 are flush with each other, and Ni is partially formed on the surface of the n + Ge layer 7. An electrode 9 is formed. Here, the photoelectric conversion layer 5 receives light incident from above on the surface of the p-Ge layer 6 and the surface of the n + Ge layer 7, and holes and electrons (hereinafter referred to as “n”) in a predetermined region of the n + Ge layer 7 by the received light. These are collectively referred to as a carrier). At this time, the photoelectric conversion layer 5 can generate an electrical signal flowing from the n + Ge layer 7 to the p-Ge layer 6 by applying a reverse bias by the application means of the output detection means.

かかる構成に加えて、この光電変換層５は、電極９を除いたn＋Ge層７の表面から、p-Ge層６の表面にかけて、膜厚が１０〜１００[nm]のGeO2膜１０が形成されている。ここで、光電変換層５の表面となるp-Ge層６の表面及びn＋Ge層７の表面と、GeO2膜１０との間の界面は、界面準位密度が1012[eV-1cm-2]以下となるように形成されており、n＋Ge層７の表面からp-Ge層６の表面にかけてリーク電流が抑制され得るようになされている。 In addition to this configuration, the photoelectric conversion layer 5 is formed with a GeO 2 film 10 having a thickness of 10 to 100 [nm] from the surface of the n + Ge layer 7 excluding the electrode 9 to the surface of the p-Ge layer 6. Has been. Here, the interface state density between the surface of the p-Ge layer 6 and the surface of the n + Ge layer 7 which is the surface of the photoelectric conversion layer 5 and the GeO 2 film 10 is 10 12 [eV −1 cm −. 2 ] It is formed so that the leakage current can be suppressed from the surface of the n + Ge layer 7 to the surface of the p-Ge layer 6.

すなわち、本発明による光電変換素子２は、光電変換層５の表面と、GeO2膜１０との界面においてトラップ準位アシスト電流が抑制し得ることにより、リーク電流が発生し難くなり、暗電流を大幅に低減し得るようになされている。因みに、ここで、暗電流とは、後述する逆バイアスをpn接合に印加したとき、光が照射されていないにもかかわらず、光電変換層５に流れてしまう電流をいう。 That is, in the photoelectric conversion element 2 according to the present invention, since the trap level assist current can be suppressed at the interface between the surface of the photoelectric conversion layer 5 and the GeO 2 film 10, a leak current is hardly generated, and a dark current is reduced. It can be greatly reduced. Incidentally, here, the dark current refers to a current that flows to the photoelectric conversion layer 5 even when light is not irradiated when a reverse bias described later is applied to the pn junction.

なお、この光検出器１は、光電変換素子２の電極９に配線１２が設けられており、この配線１２が出力検知手段３を経由して光電変換素子２の基板４に接続されている。出力検知手段３は、印加手段１３を備えており、当該印加手段１３によって光電変換素子２の電極及び基板４間に逆バイアスを印加し得るようになされている。   In the photodetector 1, a wiring 12 is provided on the electrode 9 of the photoelectric conversion element 2, and the wiring 12 is connected to the substrate 4 of the photoelectric conversion element 2 via the output detection means 3. The output detection unit 3 includes an application unit 13, and the application unit 13 can apply a reverse bias between the electrode of the photoelectric conversion element 2 and the substrate 4.

出力検知手段３は、光電変換素子２に逆バイアスを印加した状態で、当該光電変換素子２に光が入射されると、光電変換層５にてキャリアが発生したことにより生成された電気信号を、配線１２を介して検知し得るようになされている。かくして光検出器１は、出力検知手段３による電気信号の検知の有無に基づいて、光電変換素子２に入射された光を検出し得るようになされている。   When the light is incident on the photoelectric conversion element 2 in a state where a reverse bias is applied to the photoelectric conversion element 2, the output detection unit 3 outputs an electric signal generated by the generation of carriers in the photoelectric conversion layer 5. It can be detected via the wiring 12. Thus, the photodetector 1 can detect the light incident on the photoelectric conversion element 2 based on whether or not the electric signal is detected by the output detection means 3.

ここで、このような光電変換素子２については以下のようにして製造され得る。まず初めに、極性がp型のGeからなるp-Ge層６が基板４上に設けられたGeウェハ（図示せず）を用意する。次いで、イオン注入ではなく、後述する気相ドーピング法を用いて、Geウェハのp-Ge層６の表面一部にパターニングしたn＋Ge層７を形成する。   Here, such a photoelectric conversion element 2 can be manufactured as follows. First, a Ge wafer (not shown) in which a p-Ge layer 6 made of p-type Ge is provided on a substrate 4 is prepared. Next, the patterned n + Ge layer 7 is formed on a part of the surface of the p-Ge layer 6 of the Ge wafer by using a vapor phase doping method described later instead of ion implantation.

実際上、気相ドーピング法を用いる場合には、先ず初めに、Geウェハのp-Ge層６表面には、後述するGe自然酸化物を除去するクリーニングにより除去され得ない膜厚でなる所定形状のSiO2マスク（図示せず）を設けておき、当該SiO2マスクにて、n＋Ge層７が形成される接合形成予定部のみp-Ge層６表面を露出させた状態とする。次いで、露出しているp-Ge層６表面のGe自然酸化物を除去するために、HF溶液と脱イオン水とによるエッチングで、p-Ge層６の表面を複数回クリーニングした後、気相式ドーピングを行うためにGeウェハを反応炉に挿入する。 In practice, when the vapor phase doping method is used, first, the surface of the p-Ge layer 6 of the Ge wafer has a predetermined shape having a film thickness that cannot be removed by cleaning to remove a Ge native oxide described later. An SiO 2 mask (not shown) is provided, and the surface of the p-Ge layer 6 is exposed only at the junction formation planned portion where the n + Ge layer 7 is formed with the SiO 2 mask. Next, in order to remove the Ge native oxide on the exposed surface of the p-Ge layer 6, the surface of the p-Ge layer 6 is cleaned several times by etching with HF solution and deionized water, and then the vapor phase is removed. A Ge wafer is inserted into the reactor for formula doping.

Geウェハが挿入される反応炉は、炉内にH2が流されるとともに、例えば500［℃］〜700［℃］のドーピング温度に加熱される。そして、金属有機材料として、ターシャリ・ブチル・アルシン（略称：TBAs、化学式：(CH2)2CAsH2）を水素ガスに混ぜて反応炉に導入し、ドープ時間として60分、Geウェハを加熱することでドーピングする。 The reaction furnace in which the Ge wafer is inserted is heated to a doping temperature of, for example, 500 [° C.] to 700 [° C.] while H 2 flows in the furnace. Then, tertiary butyl arsine (abbreviation: TBAs, chemical formula: (CH2) 2CAsH2) as a metal organic material is mixed with hydrogen gas and introduced into the reactor, and doping is performed by heating the Ge wafer for 60 minutes as a doping time. To do.

このようにして、TBAsを用い、接合形成予定部として露出させたp-Ge層６の表面からAsを気相拡散させ、p-Ge層６の表面一部にn＋Ge層７を形成し、pn接合構造を有したGeでなる光電変換層５を形成する。次いで、p-Ge層６の表面上のSiO2マスクを除去した後、パッシベーション処理を行うことで、光電変換層５の表面にGeO2膜１０を形成し、最後に所定の手順にてGeO2膜１０を一部除去して露出させたn＋Ge層７表面に、Niで電極９を形成して光電変換素子２を製造し得る。 In this way, using TBAs, As is vapor-phase diffused from the surface of the p-Ge layer 6 exposed as the junction formation planned portion, an n + Ge layer 7 is formed on a part of the surface of the p-Ge layer 6, and pn A photoelectric conversion layer 5 made of Ge having a junction structure is formed. Then, after removing the SiO 2 mask on the surface of p-Ge layer 6, by performing the passivation process, the surfaces of the photoelectric conversion layer 5 to form a GeO 2 film 10, GeO 2 end at a predetermined procedure The photoelectric conversion element 2 can be manufactured by forming an electrode 9 of Ni on the surface of the n + Ge layer 7 exposed by removing a part of the film 10.

ここで、光電変換層５の表面にGeO2膜１０を形成するパッシベーション処理としては、酸化温度が450［℃］〜575［℃］、好ましくは550［℃］〜575［℃］で、光電変換層５の表面をドライO2ガス100％で熱酸化させることにより、p-Ge層６の表面からn＋Ge層７の表面にかけて所定の膜厚でなるGeO2膜１０を形成し得る。このようして形成されたGeO2膜１０と、光電変換層５の表面との間の界面は、低温コンダクタンス法により界面準位密度を測定すると、1012[eV-1cm-2]以下となっている。 Here, as a passivation treatment for forming the GeO 2 film 10 on the surface of the photoelectric conversion layer 5, the oxidation temperature is 450 [° C.] to 575 [° C.], preferably 550 [° C.] to 575 [° C.]. By thermally oxidizing the surface of the layer 5 with 100% dry O 2 gas, a GeO 2 film 10 having a predetermined thickness can be formed from the surface of the p-Ge layer 6 to the surface of the n + Ge layer 7. The interface between the GeO 2 film 10 thus formed and the surface of the photoelectric conversion layer 5 has an interface state density of 10 12 [eV −1 cm −2 ] or less as measured by the low-temperature conductance method. It has become.

具体的には、450［℃］の酸化温度にて光電変換層５を熱酸化させた場合、最も低い界面準位密度が1012[eV-1cm-2]以下となり得る。また、575［℃］の酸化温度にて光電変換層５を熱酸化させた場合、最も低い界面準位密度が1011[eV-1cm-2]以下となり得る。このようにしてパッシベーション処理が行われた光電変換層５の表面には、図２に示すように、光電変換層５と交わることなく、光電変換層５の表面と境界線により区切られたGeO2膜１０が形成され得る。因みに、図２は、酸化温度550［℃］で光電変換層５の表面を熱酸化させて形成したGeO2膜１０と、光電変換層（Ge層）５との界面のTEM写真を示す。 Specifically, when the photoelectric conversion layer 5 is thermally oxidized at an oxidation temperature of 450 [° C.], the lowest interface state density can be 10 12 [eV −1 cm −2 ] or less. In addition, when the photoelectric conversion layer 5 is thermally oxidized at an oxidation temperature of 575 [° C.], the lowest interface state density can be 10 11 [eV −1 cm −2 ] or less. This way, the passivation process is performed the surface of the photoelectric conversion layer 5, as shown in FIG. 2, without crossing a photoelectric conversion layer 5, GeO 2, separated by the surface and the boundary line of the photoelectric conversion layer 5 A membrane 10 can be formed. Incidentally, FIG. 2 shows a TEM photograph of the interface between the GeO 2 film 10 formed by thermally oxidizing the surface of the photoelectric conversion layer 5 at an oxidation temperature of 550 [° C.] and the photoelectric conversion layer (Ge layer) 5.

（１−２）各種検証試験
次に、酸化温度と、界面準位密度との関係について検証試験を行ったところ、図３に示すような結果が得られた。実際上、この検証試験では、４つのGeウェハを用意し、これらGeウェハをそれぞれ450［℃］、500［℃］、550［℃］又は575［℃］の異なる酸化温度で、ドライO2ガス100％により熱酸化し、GeO2膜１０を光電変換層５表面に形成した。次いで、各光電変換層５とGeO2膜１０との間の界面について、これらをGeO2／GeMOSコンデンサとして、低温コンダクタンス法により界面準位密度を調べたところ、図３に示すような結果が得られた。 (1-2) Various verification tests Next, a verification test was performed on the relationship between the oxidation temperature and the interface state density, and the results shown in FIG. 3 were obtained. In practice, in this verification test, four Ge wafers are prepared, and these Ge wafers are respectively dry O 2 gas at different oxidation temperatures of 450 [° C.], 500 [° C.], 550 [° C.] or 575 [° C.]. Thermal oxidation was performed with 100% to form a GeO 2 film 10 on the surface of the photoelectric conversion layer 5. Next, regarding the interface between each photoelectric conversion layer 5 and the GeO 2 film 10, the interface state density was examined by a low temperature conductance method using these as GeO 2 / GeMOS capacitors, and the result shown in FIG. 3 was obtained. It was.

図３から、酸化温度を450［℃］とした場合、光電変換層５とGeO2膜１０との間の最も低い界面準位密度が1012[eV-1cm-2]以下になることが確認できた。また、酸化温度を575［℃］まで上げた場合には、光電変換層５とGeO2膜１０との間の界面準位密度が全エネルギーで1012[eV-1cm-2]以下になり、最も低い界面電位密度が1011[eV-1cm-2]以下になることが確認できた。そして、酸化温度を上げてゆくことで、光電変換層５とGeO2膜１０との間の界面準位密度が、次第に低くなることが確認できた。 From FIG. 3, when the oxidation temperature is 450 [° C.], the lowest interface state density between the photoelectric conversion layer 5 and the GeO 2 film 10 may be 10 12 [eV −1 cm −2 ] or less. It could be confirmed. When the oxidation temperature is increased to 575 [° C.], the interface state density between the photoelectric conversion layer 5 and the GeO 2 film 10 becomes 10 12 [eV −1 cm −2 ] or less in total energy. It was confirmed that the lowest interface potential density was 10 11 [eV −1 cm −2 ] or less. Then, by Yuku raising the oxidation temperature, interface state density between the photoelectric conversion layer 5 and GeO 2 film 10, it was confirmed that the progressively lower.

次に、パッシベーション処理において酸化温度550［℃］でGeO2膜１０を光電変換層５の表面に形成した本発明による光電変換素子２について、暗電流と光電流とを測定したところ、図４に示すような結果が得られた。図４において、上方の波形は、0［dBm］で波長1550［nm］のレーザ光を光電変換素子２の光電変換層５に入射させたときの光電流の測定結果を示し、下方の波形は、光を照射していないときの暗電流の測定結果を示す。 Next, with respect to the photoelectric conversion element 2 according to the present invention in which the GeO 2 film 10 was formed on the surface of the photoelectric conversion layer 5 at the oxidation temperature of 550 [° C.] in the passivation treatment, dark current and photocurrent were measured. The results shown were obtained. In FIG. 4, the upper waveform shows the measurement result of the photocurrent when laser light having a wavelength of 1550 [nm] at 0 [dBm] is incident on the photoelectric conversion layer 5 of the photoelectric conversion element 2, and the lower waveform is The measurement result of the dark current when not irradiating light is shown.

因みに、この光電変換素子２は、n＋Ge層７の底面と、p-Ge層６と、の接合面積Area（図１参照）を105［μm2］とした。図４から、この光電変換素子２は、n＋Ge層７の底面と、p-Ge層６との接合面積Areaが105［μm2］であるにもかかわらず、100［nA］未満という低い暗電流を示した。このように本発明による光電変換素子２は、暗電流が低減し得、±1［V］で測られるダイオードのIon/Ioff比率がおよそ107となった。そして、このような結果は、これまで報告された値と比較して最も高い値である。 Incidentally, in this photoelectric conversion element 2, the junction area Area (see FIG. 1) between the bottom surface of the n + Ge layer 7 and the p-Ge layer 6 was set to 10 5 [μm 2 ]. From FIG. 4, this photoelectric conversion element 2 has a low darkness of less than 100 [nA] even though the junction area Area between the bottom surface of the n + Ge layer 7 and the p-Ge layer 6 is 10 5 [μm 2 ]. Current was shown. Thus, in the photoelectric conversion element 2 according to the present invention, the dark current can be reduced, and the I on / I off ratio of the diode measured by ± 1 [V] is about 10 7 . And such a result is the highest value compared with the value reported so far.

また、この光電変換素子２に波長1550［nm］のレーザ光を照射することで得られた光電流の結果から、0.5［A/W］の応答度が確認できた。因みに、図４において、‐2［V］まで逆電圧を光電変換素子２に印加しても暗電流に変化がないことは、気相ドーピング法によって形成されたn＋/p接合がほとんど欠陥を有していないことを表している。   In addition, from the result of the photocurrent obtained by irradiating the photoelectric conversion element 2 with laser light having a wavelength of 1550 [nm], a response of 0.5 [A / W] was confirmed. Incidentally, in FIG. 4, the dark current does not change even when a reverse voltage of −2 [V] is applied to the photoelectric conversion element 2, indicating that the n + / p junction formed by the vapor phase doping method has almost no defects. It means not doing.

次に、パッシベーション処理において酸化温度550［℃］でGeO2膜１０を光電変換層５上に形成した本発明による光電変換素子２について、光電変換層５に-1［V］を印加した状態で、p-Ge層６とn＋Ge層７の底面との接合面積Area（図１）と、暗電流との関係について調べたところ、図５に示すような結果が得られた。また、ここで暗電流Idarkと、接合面積Areaとを用いて、図５に示す数式から、接合電流密度Jbulkと、表面電流密度Jsurfとを算出したところ、接合電流密度Jbulkが0.032［mA/cm2］、表面電流密度Jsurfが0.27［A/cm］であった。 Next, with respect to the photoelectric conversion element 2 according to the present invention in which the GeO 2 film 10 is formed on the photoelectric conversion layer 5 at an oxidation temperature of 550 [° C.] in the passivation treatment, −1 [V] is applied to the photoelectric conversion layer 5. When the relationship between the junction area Area (FIG. 1) between the p-Ge layer 6 and the bottom surface of the n + Ge layer 7 and the dark current was examined, the result shown in FIG. 5 was obtained. In addition, when the junction current density J bulk and the surface current density J surf are calculated from the mathematical formula shown in FIG. 5 using the dark current I dark and the junction area Area, the junction current density J bulk is 0.032. [MA / cm 2 ] and the surface current density J surf were 0.27 [A / cm].

0.032［mA/cm2］という接合電流密度Jbulkは、これまで報告されているGeからなる光電変換素子の中で最も低い値の1つである。また、表面電流密度Jsurfの値も、文献１(H.Y.Yu,S.Ren,W.S.Jung,A.B.Miller,and
K.C.Saraswat,IEEE Electron Dev Letts.,vol.30,pp.1161,2009)、及び文献２（T.H.Loh,H.S.Nguyen,R.Murthy,M.B.yu,W.Y,Loh,G.Q.Lo,N.Balasubramanian,and D.L.Kwong,Appl.Phys.Lett.,vol.91,073503,2007）で報告されたものより、2桁小さいものであることが確認できた。 The junction current density J bulk of 0.032 [mA / cm 2 ] is one of the lowest values among Ge photoelectric conversion elements reported so far. The value of the surface current density J surf is also shown in Reference 1 (HYYu, S. Ren, WS Jung, ABMiller, and
KCSaraswat, IEEE Electron Dev Letts., Vol. 30, pp. 1161, 2009) and Reference 2 (THLoh, HSNguyen, R. Murthy, MByu, WY, Loh, GQLo, N. Balasubramanian, and DLKwong, Appl. Phys. Lett., Vol. 91,073503, 2007), which was confirmed to be two orders of magnitude smaller.

また、接合面積Areaを小さくした導波路型の光検出器に用いる光電変換素子について、表面電流密度Jsurfを本結果から推定することができるが、接合面積Areaが100［μm2］未満の場合は、1［nA］未満の表面電流密度Jsurfにできることが分かった。 In addition, the surface current density J surf can be estimated from this result for photoelectric conversion elements used in waveguide type photodetectors with a reduced junction area, but the junction area Area is less than 100 [μm 2 ]. Was found to be possible with a surface current density J surf of less than 1 [nA].

ここで、本発明による光電変換素子２の暗電流低減が、従来の光電変換素子とどの程度異なるかを検証するため、比較例１の光電変換素子と、比較例２の光電変換素子とを用意した。図１との対応部分に同一符号を付して示す図６に示すように、比較例１の光電変換素子１００は、上述した気相ドーピング法を用いて、600［℃］でp-Ge層６の表面一部にn＋Ge層７を形成した。また、比較例１の光電変換素子２では、温度３５０［℃］、希釈シランガスでプラズマCVD法により、p-Ge層６及びn＋Ge層７の面一の表面にパッシベーション膜としてSiO2層１０１を形成した。なお、この光電変換素子１００には、n＋Ge層７上のSiO2層１０１を一部除去し、露出させたn＋Ge層７上にNiからなる電極９を設けた。 Here, in order to verify how much the dark current reduction of the photoelectric conversion element 2 according to the present invention differs from the conventional photoelectric conversion element, the photoelectric conversion element of Comparative Example 1 and the photoelectric conversion element of Comparative Example 2 are prepared. did. As shown in FIG. 6 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, the photoelectric conversion element 100 of Comparative Example 1 is a p-Ge layer at 600 [° C.] using the above-described vapor phase doping method. An n + Ge layer 7 was formed on part of the surface of 6. In the photoelectric conversion element 2 of Comparative Example 1, the SiO 2 layer 101 is formed as a passivation film on the flush surface of the p-Ge layer 6 and the n + Ge layer 7 by a plasma CVD method with a temperature of 350 [° C.] and diluted silane gas. did. In this photoelectric conversion element 100, a part of the SiO 2 layer 101 on the n + Ge layer 7 was removed, and an electrode 9 made of Ni was provided on the exposed n + Ge layer 7.

一方、これとは別に、比較例２として、気相ドーピング法を用いずに、n＋Ge層をイオン注入により形成した光電変換素子を用意した。実際上、この比較例２の光電変換素子では、所定形状のSiO2マスクにて、n＋Ge層が形成される接合形成予定部のみp-Ge層表面を露出させた状態とし、露出したp-Ge層表面に10［eV］でリンをイオン注入した後、10［S］、600［℃］でRTA（Rapid Thermal Annealing）処理して、当該p-Ge層表面にn＋Ge層を形成した。なお、比較例２の光電変換素子は、SiO2層１０１の形成等については比較例１の光電変換素子と同じとした。 On the other hand, as Comparative Example 2, a photoelectric conversion element in which an n + Ge layer was formed by ion implantation without using the vapor phase doping method was prepared. In practice, in the photoelectric conversion element of Comparative Example 2, the surface of the p-Ge layer is exposed only at the junction formation planned portion where the n + Ge layer is formed with a SiO 2 mask having a predetermined shape, and the exposed p-Ge is exposed. After ion implantation of phosphorus at 10 [eV] on the layer surface, RTA (Rapid Thermal Annealing) treatment was performed at 10 [S] and 600 [° C.] to form an n + Ge layer on the p-Ge layer surface. The photoelectric conversion element of Comparative Example 2 was the same as the photoelectric conversion element of Comparative Example 1 with respect to the formation of the SiO 2 layer 101 and the like.

これら比較例１及び比較例２について、光を照射していないときの暗電流をそれぞれ測定したところ、図７に示すような結果が得られた。図７では、比較例１の測定結果を点線で示し、比較例２の測定結果を実線で示している。図７から、比較例１及び比較例２のいずれにおいても、本発明による光電変換素子２よりも暗電流が大きく、本発明による光電変換素子２は、比較例１の光電変換素子１００や、比較例２の光電変換素子よりも、暗電流を低減できることが確認できた。   About these comparative examples 1 and 2, when the dark current when not irradiating light was measured, the result as shown in FIG. 7 was obtained. In FIG. 7, the measurement result of Comparative Example 1 is indicated by a dotted line, and the measurement result of Comparative Example 2 is indicated by a solid line. From FIG. 7, in both Comparative Example 1 and Comparative Example 2, the dark current is larger than that of the photoelectric conversion element 2 according to the present invention, and the photoelectric conversion element 2 according to the present invention is similar to the photoelectric conversion element 100 of Comparative Example 1 and the comparison. It was confirmed that the dark current could be reduced as compared with the photoelectric conversion element of Example 2.

（１−３）動作及び効果
以上の構成において、光電変換素子２では、Geからなる光電変換層５の表面にGeO2膜１０を形成し、光電変換層５及びGeO2膜１０間の界面準位密度を1012[eV-1cm-2]以下としたことにより、光電変換層５の暗電流を低減させたり、或いは、表面再結合を抑制し得、光電変換機能を用いた各種機器の性能を従来よりも向上し得る。 (1-3) Operation and Effect In the above configuration, in the photoelectric conversion element 2, the GeO 2 film 10 is formed on the surface of the photoelectric conversion layer 5 made of Ge, and the interface state between the photoelectric conversion layer 5 and the GeO 2 film 10 is formed. By setting the unit density to 10 12 [eV −1 cm −2 ] or less, the dark current of the photoelectric conversion layer 5 can be reduced, or surface recombination can be suppressed. The performance can be improved than before.

例えば、本発明による光電変換素子２を用いた光検出器１では、光電変換層５の表面にてトラップ準位アシスト電流を大幅に抑制し得、表面リーク電流により発生する暗電流を従来よりも格段に低減でき、その結果、光電変換層５に微弱光が照射されても、暗電流が低減されている分だけ、当該微弱光に応じて生成された僅かな電気信号をも検知し得る。かくして、光検出器１では、光電変換層５にて微弱光を従来よりも検出できるようになり、光検出性能を向上し得る。   For example, in the photodetector 1 using the photoelectric conversion element 2 according to the present invention, the trap level assist current can be greatly suppressed on the surface of the photoelectric conversion layer 5, and the dark current generated by the surface leakage current can be reduced more than before. As a result, even if the photoelectric conversion layer 5 is irradiated with weak light, a slight electrical signal generated according to the weak light can be detected as much as the dark current is reduced. Thus, in the photodetector 1, weak light can be detected by the photoelectric conversion layer 5 as compared with the prior art, and the light detection performance can be improved.

（２）第２の実施の形態
図１との対応部分に同一符号を付して示す図８において、２１は第２の実施の形態による光検出器を示し、上述した第１の実施の形態による光検出器１とは異なる構成の垂直入射型の光電変換素子２２を用いている。実際上、この光電変換素子２２は、n-Geからなる光電変換層２３の表面に、Ni又はAl等の金属部材からなる第１電極２５ａ及び第２電極２５ｂが設けられている。 (2) Second Embodiment In FIG. 8, in which parts corresponding to those in FIG. 1 are denoted by the same reference numerals, reference numeral 21 denotes a photodetector according to the second embodiment, and the first embodiment described above. The vertical incident type photoelectric conversion element 22 having a configuration different from that of the photodetector 1 is used. In practice, the photoelectric conversion element 22 is provided with a first electrode 25a and a second electrode 25b made of a metal member such as Ni or Al on the surface of the photoelectric conversion layer 23 made of n-Ge.

かかる構成に加えて、光電変換層２３の表面には、これら第１電極２５ａ及び第２電極２５ｂ以外の領域にGeO2膜２６が形成されている。ここでも、光電変換層２３の表面と、GeO2膜２６との間の界面は、境界準位密度が1012[eV-1cm-2]以下となるように形成されており、光電変換層２３にてトラップ準位アシスト電流の発生が抑制され得るようになされている。これにより、光電変換層２３は、表面でのトラップ準位アシスト電流の発生が抑制されることで、表面リーク電流による暗電流の発生を低減し得るようになされている。 In addition to this configuration, a GeO 2 film 26 is formed on the surface of the photoelectric conversion layer 23 in a region other than the first electrode 25a and the second electrode 25b. Also here, the interface between the surface of the photoelectric conversion layer 23 and the GeO 2 film 26 is formed so that the boundary state density is 10 12 [eV −1 cm −2 ] or less. 23, generation of trap level assist current can be suppressed. Thereby, the photoelectric conversion layer 23 can reduce generation of dark current due to surface leakage current by suppressing generation of trap level assist current on the surface.

ここで、光電変換素子２２には、印加手段１３により第１電極２５ａ及び第２電極２５ｂ間に逆バイアスが印加され得るようになされている。光電変換素子２２は、光電変換層２３の上方から光が入射されると、当該光がGeO2膜２６を透過して当該光電変換層２３に到達し得る。これにより光電変換素子２２は、光電変換層２３にてキャリアが発生し、この際、第１電極２５ａ及び第２電極２５ｂ間に逆バイアスが印加されていることで、光電変換層２３にて発生したキャリアにより電気信号を生成し得る。かくして光検出器２１は、出力検知手段３によって光電変換素子２２にて生成される電気信号の検知の有無に基づいて、光電変換素子２２に入射された光を検出し得るようになされている。 Here, a reverse bias can be applied to the photoelectric conversion element 22 between the first electrode 25 a and the second electrode 25 b by the applying means 13. When light is incident on the photoelectric conversion element 22 from above the photoelectric conversion layer 23, the light can pass through the GeO 2 film 26 and reach the photoelectric conversion layer 23. As a result, the photoelectric conversion element 22 generates carriers in the photoelectric conversion layer 23. At this time, a reverse bias is applied between the first electrode 25 a and the second electrode 25 b, thereby generating in the photoelectric conversion layer 23. An electrical signal can be generated by the selected carrier. Thus, the photodetector 21 can detect light incident on the photoelectric conversion element 22 based on whether or not an electric signal generated by the photoelectric conversion element 22 is detected by the output detection means 3.

以上の構成において、このような光電変換素子２２を用いた光検出器２１でも、光電変換層２３の表面にてトラップ準位アシスト電流の発生を抑制し得ることから、光電変換層２３の表面で発生する表面リーク電流による暗電流を従来よりも格段に低減し得、その結果、光電変換層２３にて微弱光を従来よりも検出できるようになり、光検出器２１の光検出性能を向上し得る。   In the above configuration, even with the photodetector 21 using such a photoelectric conversion element 22, generation of trap level assist current can be suppressed on the surface of the photoelectric conversion layer 23. The dark current due to the generated surface leakage current can be remarkably reduced as compared with the conventional case. As a result, the weak light can be detected by the photoelectric conversion layer 23 as compared with the conventional case, and the light detection performance of the photodetector 21 is improved. obtain.

（３）第３の実施の形態
図９において、３１は、導波路型の光電変換素子３２を用いた光検出器を示し、上述した実施の形態とは光電変換素子３２の構成が異なるものである。なお、図９は、紙面奥側に向かう導波方向に沿って延びる導波路型の光電変換素子３２において、この光電変換素子３２の受光面断面を示す。 (3) Third Embodiment In FIG. 9, reference numeral 31 denotes a photodetector using a waveguide type photoelectric conversion element 32, and the configuration of the photoelectric conversion element 32 is different from that of the above-described embodiment. is there. FIG. 9 shows a light-receiving surface section of the photoelectric conversion element 32 in the waveguide type photoelectric conversion element 32 extending along the waveguide direction toward the back side of the drawing.

実際上、この光電変換素子３２は、導波方向に延びる帯状のSiからなる基板３３上に、SiO2層３４を介在させて同じく導波方向に延びる光電変換層３５が設けられている。光電変換層３５は、SiO2層３４の表面に形成されたp型Siでなるp-Si層３６と、このp-Si層３６の表面一部に形成されたn型Geでなるn-Ge層３７とから構成されており、n-Ge層３７の断面で光を受光し得るようになされている。 In practice, the photoelectric conversion element 32 is provided with a photoelectric conversion layer 35 extending in the waveguide direction with a SiO 2 layer 34 interposed on a substrate 33 made of strip-like Si extending in the waveguide direction. The photoelectric conversion layer 35 includes a p-Si layer 36 made of p-type Si formed on the surface of the SiO 2 layer 34, and an n-Ge made of n-type Ge formed on a part of the surface of the p-Si layer 36. The layer 37 is configured so that light can be received by the cross section of the n-Ge layer 37.

かかる構成に加えて、この光電変換層３５には、n-Ge層３７を取り囲むようにGeO2膜３９が形成されている。これにより光電変換層３５は、n-Ge層３７周辺のp-Si層３６の表面からn-Ge層３７の側面にかけてもGeO2膜３９に覆われ、n-Ge層３７及びGeO2膜３９間の界面準位密度が1012[eV-1cm-2]以下となるように形成されており、n-Ge層３７の表面からp-Si層３６の表面にかけてトラップ準位アシスト電流の発生が抑制され得るようになされている。 In addition to this configuration, a GeO 2 film 39 is formed in the photoelectric conversion layer 35 so as to surround the n-Ge layer 37. Thus, the photoelectric conversion layer 35 is also covered with the GeO 2 film 39 from the surface of the p-Si layer 36 around the n-Ge layer 37 to the side surface of the n-Ge layer 37, and the n-Ge layer 37 and the GeO 2 film 39 are covered. Between the surface of the n-Ge layer 37 and the surface of the p-Si layer 36, and the generation of the trap level assist current is generated so that the interface state density between them is 10 12 [eV −1 cm −2 ] or less. Can be suppressed.

光電変換層３５は、n-Ge層３７に図示しない電極を介して配線１２が接続された構成を有し、当該配線１２が出力検知手段３を経由してp-Si層３６に接続されている。因みに、光電変換素子３２には、印加手段１３によりn-Ge層３７及びp-Si層３６間に逆バイアスが印加されており、この状態で光電変換層３５に光が入射されると、光電変換層３５にてキャリアが発生して電気信号を生成し得る。かくして光検出器３１は、出力検知手段３によって光電変換素子３２にて生成される電気信号の検知の有無に基づいて、光電変換素子３２に入射された光を検出し得るようになされている。   The photoelectric conversion layer 35 has a configuration in which the wiring 12 is connected to the n-Ge layer 37 via an electrode (not shown), and the wiring 12 is connected to the p-Si layer 36 via the output detection means 3. Yes. Incidentally, a reverse bias is applied to the photoelectric conversion element 32 between the n-Ge layer 37 and the p-Si layer 36 by the applying means 13, and when light enters the photoelectric conversion layer 35 in this state, Carriers can be generated in the conversion layer 35 to generate an electrical signal. Thus, the photodetector 31 can detect the light incident on the photoelectric conversion element 32 based on the presence or absence of detection of an electric signal generated by the output detection means 3 in the photoelectric conversion element 32.

以上の構成において、光電変換素子３２では、光電変換層３５のp-Si層３６の表面からn-Ge層３７の表面にかけてGeO2膜３９を形成し、p-Si層３６及びGeO2膜３９間の界面準位密度を1012[eV-1cm-2]以下としたことにより、n-Ge層の側面からp-Si層３６の表面にてトラップ準位アシスト電流の発生を大幅に抑制し、表面リーク電流により発生する暗電流を従来よりも格段に低減し得る。かくして、このような光電変換素子３２でも、光電変換層３５にて微弱光を従来よりも検出できるようになり、光検出器３１の光検出性能を向上し得る。 With the above configuration, in the photoelectric conversion element 32, the GeO 2 film 39 is formed from the surface of the p-Si layer 36 of the photoelectric conversion layer 35 to the surface of the n-Ge layer 37, and the p-Si layer 36 and the GeO 2 film 39 are formed. The interfacial state density between them is set to 10 12 [eV -1 cm -2 ] or less, so that the generation of trap level assist current is greatly suppressed from the side surface of the n-Ge layer to the surface of the p-Si layer 36. In addition, the dark current generated by the surface leakage current can be remarkably reduced as compared with the conventional case. Thus, even with such a photoelectric conversion element 32, weak light can be detected by the photoelectric conversion layer 35 as compared with the conventional case, and the light detection performance of the photodetector 31 can be improved.

（４）第４の実施の形態
図９との対応部分に同一符号を付して示す図１０において、４１は導波路型の光電変換素子４２を用いた光検出器を示し、上述した実施の形態とは光電変換素子４２の構成が異なるものである。なお、図１０も、紙面奥側に向かう導波方向に沿って延びる光電変換素子４２の受光面断面を示す。 (4) Fourth Embodiment In FIG. 10, in which parts corresponding to those in FIG. 9 are assigned the same reference numerals, reference numeral 41 denotes a photodetector using a waveguide type photoelectric conversion element 42. The configuration is different from the configuration of the photoelectric conversion element 42. FIG. 10 also shows a light-receiving surface cross section of the photoelectric conversion element 42 extending along the waveguide direction toward the back side of the drawing.

実際上、この光電変換素子４２は、導波方向に延びる帯状のSiの基板３３上に、SiO2層３４及びp-Si層３６を順次介して光電変換層４３が設けられている。光電変換層４３は、p-Si層３６の表面に形成されたi-Ge層４５と、このi-Ge層４５の表面一部に形成されたn-Ge層４６と、このi-Ge層４５の表面一部に形成されn-Ge層４６と所定間隔をあけて形成されたp-Ge層４７とから構成されており、導波方向に照射される光を、同じく導波方向に延びるi-Ge層４５にて受光し得るようになされている。 In practice, this photoelectric conversion element 42 is provided with a photoelectric conversion layer 43 on a strip-like Si substrate 33 extending in the waveguide direction, with the SiO 2 layer 34 and the p-Si layer 36 sequentially disposed. The photoelectric conversion layer 43 includes an i-Ge layer 45 formed on the surface of the p-Si layer 36, an n-Ge layer 46 formed on a part of the surface of the i-Ge layer 45, and the i-Ge layer. 45 is formed of an n-Ge layer 46 formed on a part of the surface of the substrate 45 and a p-Ge layer 47 formed at a predetermined interval, and light irradiated in the waveguide direction also extends in the waveguide direction. The i-Ge layer 45 can receive light.

かかる構成に加えて、この光電変換層４３は、i-Ge層４５、n-Ge層４６及びp-Ge層４７を覆うようにしてGeO2膜４９が形成されており、i-Ge層４５及びGeO2膜４９間と、n-Ge層４５及びGeO2膜４９間と、p-Ge層４７及びGeO2膜４９間の各界面準位密度が1012[eV-1cm-2]以下となるように形成されている。 In addition to this configuration, the photoelectric conversion layer 43 includes a GeO 2 film 49 formed so as to cover the i-Ge layer 45, the n-Ge layer 46, and the p-Ge layer 47. and between the GeO 2 film 49, and between n-Ge layer 45 and the GeO 2 film 49, the interface state density between the p-Ge layer 47 and GeO 2 film 49 10 12 [eV -1 cm -2] below It is formed to become.

このように光電変換素子４２では、i-Ge層４５、n-Ge層４６及びp-Ge層４７と、GeO2膜４９との間の各界面が境界準位密度1012[eV-1cm-2]以下となるように形成されていることで、i-Ge層４５やn-Ge層４６、p-Ge層４７の表面にてトラップ準位アシスト電流の発生が抑制され得る。 Thus, in the photoelectric conversion element 42, each interface between the i-Ge layer 45, the n-Ge layer 46 and the p-Ge layer 47, and the GeO 2 film 49 has a boundary state density of 10 12 [eV −1 cm. -2 ] By forming the following, the generation of trap level assist current can be suppressed on the surfaces of the i-Ge layer 45, the n-Ge layer 46, and the p-Ge layer 47.

光電変換層４３は、n-Ge層４６に図示しない電極を介して配線１２が接続され、当該配線１２が出力検知手段３を経由して、図示しない電極を介してp-Ge層４７に接続されており、出力検知手段３の印加手段１３によって、これらn-Ge層４６及びp-Ge層４７間に逆バイアスが印加され得るようになされている。   In the photoelectric conversion layer 43, the wiring 12 is connected to the n-Ge layer 46 via an electrode (not shown), and the wiring 12 is connected to the p-Ge layer 47 via the output detection means 3 and an electrode (not shown). Thus, a reverse bias can be applied between the n-Ge layer 46 and the p-Ge layer 47 by the applying means 13 of the output detecting means 3.

光電変換素子４２は、光電変換層４３に導波方向から光が入射されると、光電変換層４３にてキャリアが発生し得、この際、印加手段１３による逆バイアスが光電変換層４３に印加されていることから、電気信号を生成し得る。かくして光検出器４１は、出力検知手段３によって光電変換素子４２にて生成される電気信号の検知の有無に基づいて、光電変換素子４２に入射された光を検出し得るようになされている。   When light is incident on the photoelectric conversion layer 43 from the waveguide direction, the photoelectric conversion element 42 can generate carriers in the photoelectric conversion layer 43. At this time, a reverse bias by the applying unit 13 is applied to the photoelectric conversion layer 43. Therefore, an electric signal can be generated. Thus, the photodetector 41 can detect light incident on the photoelectric conversion element 42 based on whether or not an electric signal generated by the photoelectric conversion element 42 is detected by the output detection means 3.

以上の構成において、光電変換素子４２では、光電変換層４３のi-Ge層４５の表面からp-Ge層４６及びn-Ge層４７の表面にかけてGeO2膜４９を形成し、光電変換層４３のi-Ge層４５、n-Ge層４６及びp-Ge層４７とGeO2膜４９との間の各界面準位密度を1012[eV-1cm-2]以下としたことにより、i-Ge層４５、n-Ge層４６及びp-Ge層４７の表面にてトラップ準位アシスト電流の発生を大幅に抑制し得、表面リーク電流により発生する暗電流を従来よりも格段に低減できる。かくして、このような光電変換素子４２でも、光電変換層４３にて微弱光を従来よりも検出できるようになり、光検出器４１の光検出性能を向上し得る。 With the above configuration, in the photoelectric conversion element 42, the GeO 2 film 49 is formed from the surface of the i-Ge layer 45 of the photoelectric conversion layer 43 to the surfaces of the p-Ge layer 46 and the n-Ge layer 47, and the photoelectric conversion layer 43. The interface state density between the iO-Ge layer 45, the n-Ge layer 46 and the p-Ge layer 47 and the GeO 2 film 49 is set to 10 12 [eV −1 cm −2 ] or less. The generation of trap level assist current can be significantly suppressed on the surfaces of the -Ge layer 45, the n-Ge layer 46, and the p-Ge layer 47, and the dark current generated by the surface leakage current can be significantly reduced as compared with the conventional case. . Thus, even with such a photoelectric conversion element 42, weak light can be detected by the photoelectric conversion layer 43 as compared with the conventional case, and the light detection performance of the photodetector 41 can be improved.

（５）第５の実施の形態
図９との対応部分に同一符号を付して示す図１１において、５１は導波路型の光電変換素子を用いた光検出器を示し、上述した実施の形態とは光電変換素子５２の構成が異なるものである。なお、図１１も、紙面奥側に向かう導波方向に沿って延びる光電変換素子５２の受光面断面を示す。 (5) Fifth Embodiment In FIG. 11, in which parts corresponding to those in FIG. 9 are assigned the same reference numerals, 51 denotes a photodetector using a waveguide type photoelectric conversion element. And the configuration of the photoelectric conversion element 52 is different. FIG. 11 also shows a light-receiving surface cross section of the photoelectric conversion element 52 extending along the waveguide direction toward the back side of the drawing.

実際上、導波方向に延びる光電変換層５５は、n-Geからなり、p-Si層３６の表面に形成され、導波方向に照射される光を受光し得るようになされている。かかる構成に加えて、この光電変換層５５には、Ni又はAl等の金属部材からなる第１電極５６ａと第２電極５６ｂとが間隔をあけて表面に設けられており、これら第１電極５６ａと第２電極５６ｂを除いた表面にGeO2膜５９が形成されている。また、光電変換層５５は、表面及びGeO2膜５９間の界面準位密度が1012[eV-1cm-2]以下となるように形成され、表面にてトラップ準位アシスト電流の発生が抑制され得るようになされている。 In practice, the photoelectric conversion layer 55 extending in the waveguide direction is made of n-Ge and is formed on the surface of the p-Si layer 36 so as to receive light irradiated in the waveguide direction. In addition to such a configuration, the photoelectric conversion layer 55 is provided with a first electrode 56a and a second electrode 56b made of a metal member such as Ni or Al on the surface at an interval, and these first electrodes 56a. A GeO 2 film 59 is formed on the surface excluding the second electrode 56b. The photoelectric conversion layer 55 is formed so that the interface state density between the surface and the GeO 2 film 59 is 10 12 [eV −1 cm −2 ] or less, and trap level assist current is generated on the surface. It can be suppressed.

ここで光電変換層５５は、第１電極５６ａに配線１２が接続され、当該配線１２が出力検知手段３を経由して第２電極５６ｂに接続されており、出力検知手段３の印加手段１３によって、これら第１電極５６ａと第２電極５６ｂ間に逆バイアスが印加され得るようになされている。   Here, in the photoelectric conversion layer 55, the wiring 12 is connected to the first electrode 56 a, and the wiring 12 is connected to the second electrode 56 b via the output detection unit 3, and the photoelectric conversion layer 55 is applied by the application unit 13 of the output detection unit 3. A reverse bias can be applied between the first electrode 56a and the second electrode 56b.

光電変換素子５２は、光電変換層５５に導波方向から光が入射されると、光電変換層５５にてキャリアが発生し得、この際、第１電極５６ａと第２電極５６ｂ間に逆バイアスが印加されていることで、電気信号を生成し得る。かくして光検出器５１は、出力検知手段３によって光電変換素子５２にて生成される電気信号の検知の有無を基に、光電変換素子５２に入射された光を検出し得るようになされている。   When light is incident on the photoelectric conversion layer 55 from the waveguide direction, the photoelectric conversion element 52 can generate carriers in the photoelectric conversion layer 55. At this time, a reverse bias is applied between the first electrode 56a and the second electrode 56b. Is applied, an electric signal can be generated. Thus, the photodetector 51 can detect light incident on the photoelectric conversion element 52 based on the presence or absence of detection of an electric signal generated by the output detection means 3 in the photoelectric conversion element 52.

以上の構成において、光電変換素子５２では、光電変換層５５の表面にGeO2膜５９を形成し、光電変換層５５の表面とGeO2膜５９との間の界面準位密度を1012[eV-1cm-2]以下としたことにより、光電変換層５５の表面にてトラップ準位アシスト電流の発生を大幅に抑制し、表面リーク電流により発生する暗電流を従来よりも格段に低減し得る。かくして、このような光電変換素子５２でも、光電変換層５５にて微弱光を従来よりも検出できるようになり、光検出器５１の光検出性能を向上し得る。 In the above configuration, in the photoelectric conversion element 52, the GeO 2 film 59 is formed on the surface of the photoelectric conversion layer 55, and the interface state density between the surface of the photoelectric conversion layer 55 and the GeO 2 film 59 is 10 12 [eV −1 cm −2 ] or less, the generation of trap level assist current can be greatly suppressed on the surface of the photoelectric conversion layer 55, and the dark current generated by the surface leakage current can be significantly reduced as compared with the conventional case. . Thus, even with such a photoelectric conversion element 52, weak light can be detected by the photoelectric conversion layer 55 as compared with the conventional case, and the light detection performance of the photodetector 51 can be improved.

（６）第６の実施の形態
図１２において、６１は太陽電池に用いられる本発明による光電変換素子を示し、光電変換層６２の受光表面がGeO2膜６８で覆われているとともに、光電変換層６２の裏面がGeO2膜６９で覆われた構成を有している。なお、この場合、太陽電池の全体図は省略し、光電変換素子６１についてのみ説明する。 (6) Sixth Embodiment In FIG. 12, reference numeral 61 denotes a photoelectric conversion element according to the present invention used for a solar cell. The light receiving surface of the photoelectric conversion layer 62 is covered with a GeO 2 film 68 and photoelectric conversion is performed. The back surface of the layer 62 is covered with a GeO 2 film 69. In this case, the overall view of the solar cell is omitted, and only the photoelectric conversion element 61 will be described.

実際上、この光電変換素子６１の光電変換層６２は、板状のGe層６４と、このGe層６４の裏面に形成されたn-Ge層６６と、同じくGe層の裏面に形成されn-Ge層６６と所定間隔をあけて配置されたp-Ge層６７とで構成されており、Ge層６４の裏面と対向する受光表面にて光を受光し得るようになされている。   In practice, the photoelectric conversion layer 62 of the photoelectric conversion element 61 includes a plate-shaped Ge layer 64, an n-Ge layer 66 formed on the back surface of the Ge layer 64, and an n-Ge layer formed on the back surface of the Ge layer. A Ge layer 66 and a p-Ge layer 67 arranged at a predetermined interval are configured so that light can be received by a light receiving surface facing the back surface of the Ge layer 64.

この実施の形態の場合、光電変換層６２は、Ge層６４、n-Ge層６６及びp-Ge層６７が面一に形成されており、これらGe層６４、n-Ge層６６及びp-Ge層６７が面一に形成された裏面にGeO2膜６９が形成されている。そして、光電変換層６２は、Ge層６４及びGeO2膜６９間の界面準位密度と、n-Ge層６６及びGeO2膜６９間の界面準位密度と、p-Ge層６７及びGeO2膜６９間の界面準位密度とが、それぞれ1012[eV-1cm-2]以下に形成されており、裏面にてキャリアの表面再結合が抑制され得るようになされている。 In the case of this embodiment, the photoelectric conversion layer 62 includes a Ge layer 64, an n-Ge layer 66, and a p-Ge layer 67 that are flush with each other, and the Ge layer 64, the n-Ge layer 66, and the p-Ge layer. A GeO 2 film 69 is formed on the back surface on which the Ge layer 67 is formed flush. The photoelectric conversion layer 62 includes an interface state density between the Ge layer 64 and the GeO 2 film 69, an interface state density between the n-Ge layer 66 and the GeO 2 film 69, a p-Ge layer 67, and GeO 2. The interface state density between the films 69 is 10 12 [eV −1 cm −2 ] or less, and the surface recombination of carriers can be suppressed on the back surface.

また、この光電変換層６２は、裏面と対向する受光表面でも、当該受光表面及びGeO2膜６８間の界面準位密度が1012[eV-1cm-2]以下に形成されており、受光表面にてキャリアの表面再結合が抑制され得るようになされている。このように、光電変換層６２は、キャリアの表面再結合が抑制されていることから、受光表面及び裏面にてキャリアが再結合してしまうことで生じる発電電圧の損失を低減して、発電効率を向上し得るようになされている。 Further, the photoelectric conversion layer 62 is formed so that the interface state density between the light receiving surface and the GeO 2 film 68 is 10 12 [eV −1 cm −2 ] or less even on the light receiving surface facing the back surface. Surface recombination of carriers can be suppressed at the surface. As described above, since the photoelectric conversion layer 62 suppresses carrier surface recombination, it reduces power generation voltage loss caused by carrier recombination on the light receiving surface and the back surface, thereby reducing power generation efficiency. Has been made to improve.

因みに、この光電変換層６２には、n-Ge層６６及びp-Ge層６７に図示しない電極を介して配線１２が接続されており、n-Ge層６６及びp-Ge層６７間に逆バイアスが印加され得る。この際、光電変換素子６１は、光電変換層６２の受光表面側から光が照射されると、光がGeO2膜６８を透過して光電変換層６２に入射され、当該光電変換層６２にてキャリアが発生し得、キャリアが発生し得ることにより電気信号を生成し得るようになされている。かくして太陽電池は、光電変換素子６１により生成された電気信号を、光電変換素子６１から配線１２を介して電気蓄積手段等に送出し得るようになされている。 Incidentally, the photoelectric conversion layer 62 is connected to the n-Ge layer 66 and the p-Ge layer 67 through an electrode (not shown), and the wiring 12 is connected between the n-Ge layer 66 and the p-Ge layer 67. A bias can be applied. At this time, when light is irradiated from the light receiving surface side of the photoelectric conversion layer 62, the photoelectric conversion element 61 is incident on the photoelectric conversion layer 62 through the GeO 2 film 68. Carriers can be generated and electric signals can be generated by the generation of carriers. Thus, the solar cell can send the electric signal generated by the photoelectric conversion element 61 from the photoelectric conversion element 61 to the electric storage means or the like via the wiring 12.

以上の構成において、光電変換素子６１では、光電変換層６２の裏面及び受光表面の両面にそれぞれGeO2膜６８,６９を形成し、光電変換層６２の裏面及びGeO2膜６９間の界面準位密度と、光電変換層６２の受光表面及びGeO2膜６８間の界面準位密度とを、それぞれ1012[eV-1cm-2]以下としたことにより、光電変換層６２の裏面及び受光表面にてキャリアの表面再結合を大幅に抑制し、その分だけ光電変換層６２での発電電圧の損失を低減できる。かくして、この光電変換素子６１では、光電変換の高効率化を実現し得、光電変換機能を用いた太陽電池の発電性能を従来よりも向上し得る。 With the above configuration, in the photoelectric conversion element 61, GeO 2 films 68 and 69 are formed on both the back surface and the light receiving surface of the photoelectric conversion layer 62, respectively, and the interface state between the back surface of the photoelectric conversion layer 62 and the GeO 2 film 69 is formed. By setting the density and the interface state density between the light receiving surface of the photoelectric conversion layer 62 and the GeO 2 film 68 to 10 12 [eV −1 cm −2 ] or less, the back surface and the light receiving surface of the photoelectric conversion layer 62 are obtained. Thus, the surface recombination of carriers can be significantly suppressed, and the loss of power generation voltage in the photoelectric conversion layer 62 can be reduced by that much. Thus, in this photoelectric conversion element 61, high efficiency of photoelectric conversion can be realized, and the power generation performance of the solar cell using the photoelectric conversion function can be improved as compared with the conventional case.

因みに、上述した実施の形態においては、光電変換層６２の裏面及び受光表面の両面にそれぞれGeO2膜６８,６９を形成するようにした場合について述べたが、本発明はこれに限らず、光電変換層６２の裏面及び受光表面のいずれか片面にだけGeO2膜を形成するようにしてもよい。このような光電変換素子であっても、GeO2膜の形成面とGeO2膜との間の界面準位密度を1012[eV-1cm-2]以下とすることで、当該GeO2膜の形成面にてキャリアの表面再結合を抑制し得る。 Incidentally, in the above-described embodiment, the case where the GeO 2 films 68 and 69 are respectively formed on both the back surface and the light receiving surface of the photoelectric conversion layer 62 has been described. A GeO 2 film may be formed on only one of the back surface and the light receiving surface of the conversion layer 62. Even with such a photoelectric conversion element, by the interface state density between the forming surface and the GeO 2 film of GeO 2 film with 10 12 [eV -1 cm -2] Hereinafter, the GeO 2 film The surface recombination of the carrier can be suppressed at the formation surface of.

（７）他の実施の形態
なお、本発明は、本実施形態に限定されるものではなく、本発明の要旨の範囲内で種々の変形実施が可能であり、上述した実施の形態を組み合わせた構成であってもよい。また、上述した実施の形態においては、熱酸化により、例えば光電変換層５の表面にGeO2膜１０を形成し、光電変換層５及GeO2膜１０間の界面準位密度を1012[eV-1cm-2]以下にするようにした場合について述べたが、本発明はこれに限らず、例えばECR（Electron Cyclotron Resonance）プラズマにより光電変換層５の表面にGeO2膜１０を形成し、光電変換層５及GeO2膜１０間の界面準位密度を1012[eV-1cm-2]以下にするようにしてもよい。すなわち、本発明では、他の実施の形態においても、光電変換層及GeO2膜間の界面準位密度を1012[eV-1cm-2]以下にできれば、その他種々の方法にて光電変換層の表面にGeO2膜を形成してもよい。 (7) Other Embodiments The present invention is not limited to the present embodiment, and various modifications can be made within the scope of the gist of the present invention, and the above-described embodiments are combined. It may be a configuration. In the above-described embodiment, for example, the GeO 2 film 10 is formed on the surface of the photoelectric conversion layer 5 by thermal oxidation, and the interface state density between the photoelectric conversion layer 5 and the GeO 2 film 10 is 10 12 [eV -1 cm -2 ] or less, the present invention is not limited to this. For example, the GeO 2 film 10 is formed on the surface of the photoelectric conversion layer 5 by ECR (Electron Cyclotron Resonance) plasma, The interface state density between the photoelectric conversion layer 5 and the GeO 2 film 10 may be 10 12 [eV −1 cm −2 ] or less. That is, in the present invention, in other embodiments, as long as the interface state density between the photoelectric conversion layer and the GeO 2 film can be 10 12 [eV −1 cm −2 ] or less, photoelectric conversion can be performed by various other methods. A GeO 2 film may be formed on the surface of the layer.

１,２１,３１,４１,５１ 光検出器
２,２２,３２,４２,５２,６１ 光電変換素子
５,２３,３５,４３,５５,６２ 光電変換層
１０,２６,３９,４９,５９ GeO2膜
６,４７,６７ p-Ge層（第２極性半導体層）
７,３７,４６,６６ n-Ge層（第１極性半導体層）
３６ p-Si層（第２極性半導体層） 1, 21, 31, 41, 51 Photodetector 2, 22, 32, 42, 52, 61 Photoelectric conversion element 5, 23, 35, 43, 55, 62 Photoelectric conversion layer 10, 26, 39, 49, 59 GeO 2 films 6, 47, 67 p-Ge layer (second polar semiconductor layer)
7, 37, 46, 66 n-Ge layer (first polar semiconductor layer)
36 p-Si layer (second polar semiconductor layer)

Claims (7)

Geを含む光電変換層と、前記光電変換層の表面に形成されたGeO2膜とを備え、
前記光電変換層及び前記GeO2膜間の界面準位密度が1012[eV-1cm-2]以下である
ことを特徴とする光電変換素子。 A photoelectric conversion layer containing Ge, and a GeO 2 film formed on the surface of the photoelectric conversion layer,
The photoelectric conversion element, wherein an interface state density between the photoelectric conversion layer and the GeO 2 film is 10 12 [eV −1 cm −2 ] or less. 前記光電変換層は、p型又はn型の第１の極性からなる第１極性半導体層と、該第１極性半導体層とは逆極性のn型又はp型の第２の極性からなる第２極性半導体層とが隣接又は非隣接に配置され、
前記第１極性半導体層及び前記第２極性半導体層は、少なくともいずれか一方が前記Geからなる
ことを特徴とする請求項１記載の光電変換素子。 The photoelectric conversion layer includes a first polarity semiconductor layer having a p-type or n-type first polarity, and a second polarity having an n-type or p-type second polarity opposite to the first polarity semiconductor layer. The polar semiconductor layer is arranged adjacent or non-adjacent,
The photoelectric conversion element according to claim 1, wherein at least one of the first polar semiconductor layer and the second polar semiconductor layer is made of Ge. 前記光電変換層は、前記第１極性半導体層と前記第２極性半導体層とが面一に配置され、前記面一の表面に前記GeO2膜が形成されている
ことを特徴とする請求項２記載の光電変換素子。 The photoelectric conversion layer is characterized in that the first polar semiconductor layer and the second polar semiconductor layer are arranged flush with each other, and the GeO 2 film is formed on the flush surface. The photoelectric conversion element as described. 前記光電変換層は、前記第２極性半導体層上に前記第１極性半導体層を備え、
前記GeO2膜は、前記第１極性半導体層を覆うように形成されているとともに、前記第２極性半導体層の表面から前記第１極性半導体層の側面にかけても形成されている
ことを特徴とする請求項２記載の光電変換素子。 The photoelectric conversion layer includes the first polar semiconductor layer on the second polar semiconductor layer,
The GeO 2 film is formed so as to cover the first polar semiconductor layer, and is also formed from the surface of the second polar semiconductor layer to the side surface of the first polar semiconductor layer. The photoelectric conversion element according to claim 2. 請求項１〜４のうちいずれか１項記載の光電変換素子と、
前記光電変換素子が光を受光することにより該光電変換素子から出力される出力信号を検知する出力検知手段と
を備えたことを特徴とする光検出器。 The photoelectric conversion element according to any one of claims 1 to 4,
An optical detector comprising: an output detection unit configured to detect an output signal output from the photoelectric conversion element when the photoelectric conversion element receives light. 光電変換素子が光を受光することにより該光電変換素子にて電気信号を生成する太陽電池であって、
前記光電変換素子が請求項１〜４のうちいずれか１項記載の光電変換素子である
ことを特徴とする太陽電池。 A solar cell that generates an electrical signal in the photoelectric conversion element when the photoelectric conversion element receives light,
The said photoelectric conversion element is a photoelectric conversion element of any one of Claims 1-4. The solar cell characterized by the above-mentioned. 前記光電変換素子には、電極が配置された裏面と、光を受光する受光表面との両面に前記GeO2膜がそれぞれ形成されている
ことを特徴とする請求項６記載の太陽電池。 The solar cell according to claim 6, wherein the photoelectric conversion element has the GeO 2 film formed on both a back surface on which electrodes are arranged and a light receiving surface that receives light.
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JPS5891686A (en) * 1981-11-27 1983-05-31 Nec Corp Germanium semiconductor device and its manufacture
JPS58119675A (en) * 1982-01-11 1983-07-16 Nec Corp Germanium semiconductor element
JPS63258079A (en) * 1987-04-15 1988-10-25 Fujitsu Ltd Semiconductor photodetector
JP2000164841A (en) * 1998-10-09 2000-06-16 Stmicroelectronics Srl Infrared detector device and process for forming the same
JP2004071763A (en) * 2002-08-05 2004-03-04 Toyota Motor Corp Photovoltaic element

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5891686A (en) * 1981-11-27 1983-05-31 Nec Corp Germanium semiconductor device and its manufacture
JPS58119675A (en) * 1982-01-11 1983-07-16 Nec Corp Germanium semiconductor element
JPS63258079A (en) * 1987-04-15 1988-10-25 Fujitsu Ltd Semiconductor photodetector
JP2000164841A (en) * 1998-10-09 2000-06-16 Stmicroelectronics Srl Infrared detector device and process for forming the same
JP2004071763A (en) * 2002-08-05 2004-03-04 Toyota Motor Corp Photovoltaic element

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