JPH0791155B2 - Method for producing CdTe single crystal - Google Patents
Method for producing CdTe single crystalInfo
- Publication number
- JPH0791155B2 JPH0791155B2 JP2210276A JP21027690A JPH0791155B2 JP H0791155 B2 JPH0791155 B2 JP H0791155B2 JP 2210276 A JP2210276 A JP 2210276A JP 21027690 A JP21027690 A JP 21027690A JP H0791155 B2 JPH0791155 B2 JP H0791155B2
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- JP
- Japan
- Prior art keywords
- crystal
- resistivity
- single crystal
- heat treatment
- present
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Measurement Of Radiation (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
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Description
【発明の詳細な説明】 発明の技術分野 本発明は、放射線検出素子用等として有用な高抵抗CdTe
単結晶の製造方法に関する。Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a high resistance CdTe useful as a radiation detecting element and the like.
The present invention relates to a method for producing a single crystal.
従来技術 CdTe単結晶は放射線検出素子等に有用であり、その特性
向上、特に高エネルギー分解能化をめざして従来からCd
Te単結晶の製造方法が検討されている。Conventional technology CdTe single crystals are useful for radiation detectors, etc.
A method for producing a Te single crystal is being studied.
高エネルギー分解能を達成するための結晶特性として
は、主に次の２点が重要である。The following two points are important as crystal characteristics for achieving high energy resolution.
第１点は、抵抗率が高いことである。抵抗率が低いと放
射線検出器の信号ノイズが増大し好ましくなく、１×10
8Ωcm以上の値が必要である。第２点はキャリアライフ
タイムが大きいことである。キャリアライフタイムが小
さいと、キャリア収集効率が低下し、エネルギー分解能
が低下する。The first point is that the resistivity is high. If the resistivity is low, the signal noise of the radiation detector increases, which is not desirable, and 1 × 10
A value of 8 Ωcm or more is required. The second point is that the carrier lifetime is long. When the carrier lifetime is short, the carrier collection efficiency is lowered and the energy resolution is lowered.
以上のことから、放射線検出素子用の結晶の製造条件の
検討は、高抵抗率化、キャリアライフタイムの増大の２
点に注目して行なわれてきた。From the above, the examination of the manufacturing conditions of the crystal for the radiation detection element was conducted in order to increase the resistivity and increase the carrier lifetime.
It was done paying attention to the points.
第１点目の高抵抗率化に対しては、結晶成長時に塩素を
ドープして抵抗率を向上する事が報告されている。It has been reported that chlorine is doped at the time of crystal growth to improve the resistivity in order to increase the first resistivity.
第２点目のキャリアライフタイムの増大に関しては、結
晶の純度の向上によって達成される事が報告されてい
る。It has been reported that the second point, the increase in carrier lifetime, is achieved by improving the crystal purity.
本発明が解決する問題点 従来から、高抵抗率の結晶を得るためには、結晶中に添
加する塩素濃度を増加することが効果あることが知られ
ている。しかし、塩素濃度が高くなるほどキャリアライ
フタイムは低下する傾向があるために、放射線検出素子
に適した充分抵抗率が高く、しかもキャリアライフタイ
ムも大きい結晶を得ることが出来ないという問題点があ
った。すなわち、放射線検出素子として使用可能な抵抗
率を得るためには、塩素の添加量をある程度大きな量に
せざるを得ず、そのため、キャリアライフタイムが小さ
くなり、結果的に、この結晶を使用して作製した放射線
検出素子のエネルギー分解能は満足できる値が得られて
いないという問題があった。Problems to be Solved by the Present Invention It has been conventionally known that increasing the concentration of chlorine added to a crystal is effective for obtaining a crystal having a high resistivity. However, since the carrier lifetime tends to decrease as the chlorine concentration increases, there is a problem that it is not possible to obtain a crystal having a sufficiently high resistivity suitable for a radiation detection element and a large carrier lifetime. . That is, in order to obtain a resistivity that can be used as a radiation detection element, the amount of chlorine added has to be large to some extent, so that the carrier lifetime becomes small, and as a result, this crystal is used. There has been a problem that a satisfactory value has not been obtained for the energy resolution of the manufactured radiation detection element.
発明の構成 本発明は、上記の問題点を解決したものであって、放射
線検出素子用のCdTe単結晶の製造方法において、塩素を
0.8重量ppm以上５重量ppm以下の濃度で添加したCdTe単
結晶を、真空中、あるいは不活性ガス中で350℃以上450
℃以下の温度で熱処理することを特徴とするCdTe単結晶
の製造方法に関するものである。Structure of the Invention The present invention is to solve the above problems, in the method for producing a CdTe single crystal for a radiation detection element, chlorine
CdTe single crystal added at a concentration of 0.8 wtppm or more and 5 wtppm or less is heated in vacuum or in an inert gas at 350 ° C or higher and 450 ° C or higher.
The present invention relates to a method for producing a CdTe single crystal, which is characterized by performing a heat treatment at a temperature of ℃ or less.
問題点を解決するための手段および作用 上記の問題点を解決するためには、低塩素濃度でも抵抗
率の高い結晶を得る方法が必要であり、本発明者等は、
結晶を熱処理することで抵抗率が増加することを新たに
見い出し、本発明に至ったものである。Means and Actions for Solving the Problems In order to solve the above problems, a method for obtaining a crystal having a high resistivity even at a low chlorine concentration is necessary.
The present invention has been newly found that the resistivity is increased by heat-treating the crystal, and the present invention has been achieved.
本発明における熱処理は真空中あるいはAr、窒素などの
不活性ガス雰囲気下で行う。これは、酸化防止のために
行なわれる。The heat treatment in the present invention is performed in vacuum or in an atmosphere of an inert gas such as Ar or nitrogen. This is done to prevent oxidation.
本発明における熱処理温度は350℃以上450℃以下である
必要がある。熱処理温度が350℃未満であっても、450℃
を越えても、抵抗率は１×108Ωcm以下となるため好ま
しくないからである。特に結晶中の塩素濃度が小さい場
合、この熱処理温度範囲はより一層狭く限定される。例
えば、第１図に示すように塩素濃度が１重量ppmの結晶
の場合、370℃以上400℃以下で熱処理する必要がある。
しかし、塩素濃度が５重量ppmの結晶の場合、熱処理温
度範囲は350℃以上450℃以下で熱処理することで抵抗率
は１×108Ωcm以上となる。The heat treatment temperature in the present invention needs to be 350 ° C. or higher and 450 ° C. or lower. 450 ℃ even if the heat treatment temperature is less than 350 ℃
If it exceeds, the resistivity will be 1 × 10 8 Ωcm or less, which is not preferable. Especially when the chlorine concentration in the crystal is small, this heat treatment temperature range is further narrowed and limited. For example, as shown in FIG. 1, in the case of a crystal having a chlorine concentration of 1 wtppm, it is necessary to perform heat treatment at 370 ° C or higher and 400 ° C or lower.
However, in the case of a crystal having a chlorine concentration of 5 ppm by weight, the resistivity becomes 1 × 10 8 Ωcm or more when heat treatment is performed at a temperature range of 350 ° C. to 450 ° C.
本発明の熱処理は、例えば第２図に示すごとく、塩素が
0.8重量ppm以上、５重量ppm以下の濃度で添加された結
晶に対して行われる。0.8重量ppm未満では本発明の熱処
理を行っても、結晶の抵抗率は１×108Ωcm以上に向上
しないため、放射線検出素子用の結晶として使用するこ
とが出来ない。５重量ppmを越える場合は、例えば第３
図に示すごとく、本発明の熱処理を行っても、キャリア
ライフタイムが低くなるため、高性能の放射線検出素子
が得られないため効果が少ない。In the heat treatment of the present invention, for example, as shown in FIG.
It is performed on crystals added at a concentration of 0.8 wtppm or more and 5 wtppm or less. If it is less than 0.8 ppm by weight, the resistivity of the crystal does not improve to 1 × 10 8 Ωcm or more even if the heat treatment of the present invention is performed, and therefore it cannot be used as a crystal for a radiation detecting element. When it exceeds 5 ppm by weight, for example, the third
As shown in the figure, even if the heat treatment of the present invention is performed, the carrier lifetime becomes short, and a high-performance radiation detecting element cannot be obtained, so that the effect is small.
本発明の熱処理時間は、１時間以上、より好ましくは15
時間以上である。尚、該熱処理はインゴットの状態で
も、ウエハーの状態で行なっても良い。The heat treatment time of the present invention is 1 hour or more, more preferably 15 hours.
More than time. The heat treatment may be performed in the ingot state or the wafer state.
［実施例］ 塩素濃度１重量ppmのCdTe結晶ウエハーを、真空中で385
℃で15時間熱処理した後、約50℃/hrで室温まで炉冷し
た結晶を用いて、放射線検出素子を作製した。[Example] A CdTe crystal wafer having a chlorine concentration of 1 wtppm was subjected to 385 vacuum treatment.
A radiation detection element was produced using a crystal that was heat-treated at 15 ° C. for 15 hours and then furnace-cooled to room temperature at about 50 ° C./hr.
この結晶の抵抗率は、２×108Ωcm、キャリアライフタ
イムは電子が１μs,ホールが0.5μｓであった。このよ
うに本発明の処理品は、高抵抗、高キャリアライフタイ
ムを同時に満足するものであった。The resistivity of this crystal was 2 × 10 8 Ωcm, and the carrier lifetime was 1 μs for electrons and 0.5 μs for holes. As described above, the treated product of the present invention satisfied both high resistance and high carrier lifetime.
さらに放射線検出素子としての特性は、241Amの放射線
（59.5keVのエネルギーをもっている）を測定したとき
のピーク強度半値幅が、印加電圧15Vにおいて5keVの良
好な分解能が得られた。Furthermore, the characteristics of the radiation detection element were that the peak intensity half-width when measuring 241 Am radiation (having an energy of 59.5 keV) was 5 keV at an applied voltage of 15 V.
［比較例１］ 塩素濃度１重量ppmの結晶を、熱処理をせずに放射線検
出素子を作製した。この結晶の抵抗率は、１×104Ωcm
と低く、そのためキャリアライフタイムも測定出来なか
った。放射線検出素子としての特性は、抵抗率が低すぎ
たために、リーク電流が大きく、241Amの放射線を測定
したところ、なんらスペクトルが得られなかった。[Comparative Example 1] A crystal having a chlorine concentration of 1 ppm by weight was subjected to no heat treatment to prepare a radiation detecting element. The resistivity of this crystal is 1 × 10 4 Ωcm
It was so low that the carrier lifetime could not be measured. Regarding the characteristics of the radiation detection element, the resistivity was too low, so the leak current was large, and when a radiation of 241 Am was measured, no spectrum was obtained.
発明の効果 本発明により、結晶中塩素濃度が0.8重量ppm以上５重量
ppm以下という低塩素濃度でも、放射線検出素子を作製
するのに充分な抵抗率の高い結晶を得ることが出来るよ
うになった。このため、この結晶を用いて、従来よりも
エネルギー分解能の良好な放射線検出素子を作製するこ
とができるようになる。Effect of the Invention According to the present invention, the chlorine concentration in the crystal is 0.8 wt ppm or more and 5 wt.
Even with a low chlorine concentration of ppm or less, it has become possible to obtain a crystal having a high resistivity enough to manufacture a radiation detection element. Therefore, using this crystal, it becomes possible to fabricate a radiation detection element having a better energy resolution than ever before.
第１図は熱処理温度による抵抗率の変化を示したもので
ある。 第２図は結晶中の塩素濃度と熱処理によって得られた抵
抗率の関係を示したものである。 第３図は結晶中の塩素濃度とキャリアライフタイムの関
係を示したものである。FIG. 1 shows the change in resistivity depending on the heat treatment temperature. FIG. 2 shows the relationship between the chlorine concentration in the crystal and the resistivity obtained by heat treatment. FIG. 3 shows the relationship between the chlorine concentration in the crystal and the carrier lifetime.
Claims (1)
において、塩素を0.8重量ppm以上５重量ppm以下の濃度
で添加したCdTe単結晶を、真空中、あるいは不活性ガス
中で350℃以上450℃以下の温度で熱処理することを特徴
とするCdTe単結晶の製造方法。1. A method for producing a CdTe single crystal for a radiation detecting element, wherein the CdTe single crystal to which chlorine is added at a concentration of 0.8 wtppm or more and 5 wtppm or less is 350 ° C. or more in a vacuum or in an inert gas. A method for producing a CdTe single crystal, which comprises performing heat treatment at a temperature of 450 ° C. or lower.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2210276A JPH0791155B2 (en) | 1990-08-10 | 1990-08-10 | Method for producing CdTe single crystal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2210276A JPH0791155B2 (en) | 1990-08-10 | 1990-08-10 | Method for producing CdTe single crystal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0497990A JPH0497990A (en) | 1992-03-30 |
| JPH0791155B2 true JPH0791155B2 (en) | 1995-10-04 |
Family
ID=16586712
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2210276A Expired - Lifetime JPH0791155B2 (en) | 1990-08-10 | 1990-08-10 | Method for producing CdTe single crystal |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0791155B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06345598A (en) * | 1993-06-04 | 1994-12-20 | Japan Energy Corp | Cdte crystal for radiation detecting element and its production |
-
1990
- 1990-08-10 JP JP2210276A patent/JPH0791155B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0497990A (en) | 1992-03-30 |
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