591226 玖、發明說明（1 ) 【發明所屬之技術領域】 本發明是有關於一種氫氣感測器，特別是指一種二極 體式氫氣感測器。 【先前技術】 5 氫氣感測器已大量使用於工廠、實驗室、醫院以及 運輸工具中，以達到預警的效果。 目前傳統的氫氣感測器，大部分是屬於被動式元件 的氫氣感測器，尚須與其他的附加設備或轉換電路才能進 行氫氣濃度的分析或放大，因此造成體積必須加大、價格 10 昂貴，而且無法達到智慧化的要求。 半導體氫氣感測器以結構而言，可概分為金屬-半導 體蕭特基能障二極體、金屬—氧化層—半導體肖特基能障二 極體、金屬-氧化層—半導體電容，以及金屬—氧化層—半導 體場效電晶體等四類，電晶體式氫氣感測器主要是以臨限 15 電壓（threshold voltage)與兩端電容值的改變，來作 為感測氫氣的依據，但其製作成本較高，而且感測的靈敏 度也較小’而一極體式氫氣感測器，由於在運用上可擷取 與電壓的關係呈現指數的變化順向電流，所以電流的改變 篁較大’而可得到較大之氫氣感測靈敏度，同時，由於其 20 逆向電流呈現高線性度與高靈敏度，因此，二極體式氫氣 感測器更適合於商業應用。 但疋’ 一極體式氫氣感測器一般是以石夕為主要材料 ’而石夕材料最大的缺點是無法在高溫環境下使用，且其靈 敏度較低，雖然，目前已可以砷化鎵、磷化銦、氮化鎵及 6 玖、發明說明C; 2、）：:: 碳化石夕等化合物半導體材料解決這個問題，但是，石申化錄 和鱗化銦等化合物半導體材料材料必須在低溫區操作，才 會具有較大的靈敏度，氮化鎵及碳化石夕等化合物半導體材 料則需要在高溫下操作，因此，石申化嫁、鱗化姻、氣化録 及礙化石夕等化合物半導體材料仍無法提供足夠的工作溫度 區間’解決感測靈敏度的問題。 雖然’目前已知使㈣化銦鎵化合物半導體材料， 可以提供較大的工作溫度範圍操作，然而，礙化鋼嫁材料 僅能固定在銦的莫爾分率為0·49之條件下，才能與碎化 蘇基板作晶格匹配，因此仍然有使用的極大限制。所以， 如何使二極體式氳氣感測器的工作溫度區間增加、感測靈 敏度提咼，疋當前業界與學界共同努力的目標。 【發明内容】 因此，本發明之目的，即在提供一種低漏電流，並具 有高感測靈敏度之氫氣感測器。 於是，本發明之一種氫氣感測器，包含一半導體基板 、一形成於該半導體基板上的半導體緩衝層、一形成於該 半導體緩衝層上的半導體薄膜層、一形成於該半導體薄膜 層上邛刀區域的半導體歐姆接觸頂層、一作為陰極電極的 歐姆金屬接觸層，及一作為陽極電極的蕭特基金屬接觸層 ，忒歐姆金屬接觸層形成於該半導體歐姆接觸頂層上部分 區域且向下延伸至該半導體歐姆接觸頂層與該半導體薄膜 層，該蕭特基金屬接觸層形成於該半導體薄膜層上之部分 區域且與該半導體歐姆接觸頂層不相接觸；當氫氣接觸蕭 玖、發明說明（3 y :「 特基金屬接觸層後被解離成氫原子，而在該半導體薄臈層 界面造成極化作用形成偶極矩層，進而改變蕭特基能障之 向度而可改變元件的電流·電壓特性，以感測氫氣濃度。 【實施方式】 本發明之前述以及其他技術内容、特點與功效，在以 下配口參考圖式之一較佳實施例的詳細說明中，將可清楚 的明白。 參閱第一圖，本發明一種氫氣感測器之一較佳實施例 ，適用於感測氫氣濃度，包含一半導體基板u、一形成 於該半導體基板11上的半導體緩衝層12、一形成於該半 導體緩衝層12上的半導體薄膜層13、一形成於該半導體 薄膜層13上部分區域的半導體歐姆接觸頂層Μ、一形成 於該半導體歐姆接觸頂層14上部分區域且向下延伸至該 半導體歐姆接觸頂層14與該半導體薄膜層13的歐姆金屬 接觸層15、-幵，成於該半導體薄膜層13上部分區域且與 該半導體歐姆接觸頂層14不相接觸之氧化層16，及一形 成於該氧化層16上且與該半導體歐姆接觸頂層14不相接 觸的蕭特基金屬接觸層17。 上述氫氣感測器1是選用一半絕緣型砷化鎵（GaAs)M 料作為該半導體基& 11，並利用金屬有機化學氣相沉積 (MOCVD)或分子束磊晶成長法（MBE)的技術，並選用未摻雜 之砷化鎵（GaAs)材料，在該半導體基板u上成長〇.丨至 5-0糾1，形成該半導體緩衝層12;接著可選用n型、濃度 範圍介於1χ10ΐ5至5xl0iW3之間、紹的莫爾分率介“ 玖、發明說明Γ4 ) 彳 :/ 至0.45之間的神化銘鎵（AixGai-xAs)材料，及/或n型、 濃度範圍介於lxl〇15至5xl0i8cm-3之間、銦的莫爾分率為 0.49的磷化銦鎵（inxGai-xp)材料，在該半導體緩衝層12 上成長厚度1000至5000A，形成該半導體薄膜層13。 接著，選用η型、濃度範圍介於1χ1〇π至lxl〇19cnf3 之間砷化鎵（GaAs)材料，在該半導體薄膜層13上部分區 域成長厚度100至3000A，形成該半導體歐姆接觸頂層 14。然後，利用傳統光罩微影姓刻及真空蒸鍵的技術，選 用金-鍺-鎳合金（AuGeNi)材料，及/或金—鍺合金（AuGe)， 於該半導體歐姆接觸頂層14上蒸鍵一厚度麵A至_ 之間的合金層，並在40(rc之環境下退火i分鐘，使該合 金層向下貝穿該半導體歐姆接觸頂層14，並延伸至該半 導體薄膜層13，形成該歐姆金屬接觸層15。 然後’選帛一氧化石夕（Si〇2)、三氧化鈦（丁⑼），及/或 氧化辞(Zn〇)，在該半導體薄膜層13上部分區域與該半導 體歐姆接觸頂層14不相接觸地成長厚度20至5〇〇A，形 成該氧化^16;最後，再選用鉑(pt)、鈀⑽)、鎳(Ni) 、雜h)、釕（Ru) ’及/或銀（Ir)其中之一種，在該氧化 曰16上频iggA至2μιη，形成該作為陽極電極之蕭特基 金屬接觸層17，製備完成本發明氫氣感測器卜 由於始、飽、链、蚀 . _… 鎳鍺、釕，及/或銥等金屬對氫氣具 有良好的觸媒活性’所以當氫氣分子吸附於其表面時會被 =離為氫原子，同時，大部分的氫原子將會擴散穿透此蕭 、基金屬㈣17’而該些氯原子擴散至蕭特基金屬接 591226 玖、發明說明（5 ) 觸層17與氧化層16之界面時，會造成極化作用而形成一 偶極矩層，此偶極矩層可改變蕭特基金屬接觸層17與氧 化層16之界面的電場，進而降低了金屬—半導體接面之蕭 特基能障高度，因此可改變本發明氫氣感測器丨之電流_ 5 電壓特性，而達到感測氫氣之目的。 參閱第二圖，說明本發明氫氣感測器1於感測到氫氣 時的能帶變化，並以蕭特基金屬接觸層17以鈀金屬為材 料而與氫氣作用為例。在引入氳氣之後，由於鈀金屬對氫 氣具有觸媒作用，當氫分子被吸附於鈀金屬表面時會被解 1〇 離為氫原子，大部分氫原子將會擴散穿透鈀金屬，並於蕭 特基金屬接觸層17與氧化層16界面間形成偶極矩層，此 偶極矩層將改變原有電荷分佈之平衡狀態，而達到新的平 衡狀態，此一新的平衡狀態減少了半導體的空乏區寬度， 進而降低了蕭特基能障高度。 15 參閱第三圖，上述氫氣感測器1於室溫時在不同氫氣 含量 air、15、48、97、202、1010，及 9090 ppm H2/air 之環境下所測量之順向電流-電壓特性曲線結果，由上述 可知，氫氣含量愈大，蕭特基能障高度愈小，因此通過界 面電流將會相對愈大；由實驗結果可知，本發明氳氣感測 器1於室溫情況下能感應到極低濃度15ppm HVair之氮 氣含量，而且電流的變化量在順偏壓0.2伏特時更可從 1〇_12安培改變至10·9安培，而具有極高的感測能力。 第四圖是紀錄本發明氫氣感測器1在室溫時對不同氮 氣濃度的蕭特基能障高度變化的實驗結果，由此圖可明顯 10 591226 玖、發明說明（6 ) 看到，當氫氣濃度越高時，所引起的能障高度變化越大。 第五圖是本發明氫氣感測器1之溫度對飽和靈敏度影· 響的實驗結果，飽和靈敏度s定義為電流變化量對基準電 流之比值，亦即扣(\一4)/4，其中I”、Iair分別為氫氣 5 環丨兄下以及二氧中的電流值，由此圖可知，本發明氫氣减 測器1之靈敏度隨氫氣含量增加而增加，且在室溫、順向 偏壓為0.35V，及9090ppm的·氫氣含量環境下，飽和靈敏 度更高達156,而隨著溫度升高，因為能障高度變化量逐 漸變小，飽和靈敏度也跟著變小。 10 第六圖是本發明氫氣感測器1於95°C時對不同氫氣 含篁㈣、15、97、1010，及9〇9〇Ppm H2/air)之環境下所 測量之電流-電壓特性曲線圖，在順向偏壓時，電流呈現 指數變化，於順向偏壓〇·2伏特時仍有一百倍的變化量， 在逆向偏壓時則呈現線性變化，且變化量也都有一百倍以 15上，證明本發明氫氣感測器i於高溫的情況下感應仍相當 明顯，並在應用方面相當穩定。 參閱第七圖，本發明氫氣感測器1在溫度為95°c時 所測量之暫態響應的實驗結果，圖中所示點a與點b分別 代表氮氣的引入及關閉氫氣之瞬間操作點。當氫氣引入時 20 ，代表不同氫氣含量的空氣《 500ml/min的速率流入測試 腔中’測試條件為維持_固定順向偏M vf=().35v，由於 解離之氫原子形成偶極化矩，電流因為氮氣的導入迅速增 加，另方面，s氫氣關閉時，感測器直接暴露於空氣中 ’虱原子結合為氫分子，或與氧結合為水分子而脫附於蕭 11 591226 玖、發明說明（7 ) 特基金屬接觸層17表面，因而又造成對應電流的回復。 若定義反應時間為達到穩定值所需之時間，則由圖可 知’本發明氫氣感測器1之反應時間約為302(15ppm H2/aii〇、40.3(202ppm H2/air)、13.2(l〇l〇ppm H2/air)， 5 以及4·5秒（9090PPm H2/air)，顯示本發明氫氣感測器丄 在氫氣的濃度越高時，碰撞的機率相對較高，而且電流的 變化較大，意即愈靈敏。 綜上述，由於砷化鋁鎵（AlGaAs)材料具有較大的能隙 ，及跟砷化鎵晶格相匹配之優點，因此使得本發明氫氣感 10 測器1以半絕緣型砷化鎵（GaAs)材料作為半導體基板u ，並配合砷化鋁鎵、磷化銦鎵等材料成長成半導體薄膜層 13,及選用η型砷化鎵（GaAs)為半導體歐姆接觸頂層14 ，因而在工程設計及應用上甚具彈性；而且，本發明氫氣 感測器1之半導體歐姆接觸頂層14,除了可以達到降低 15 電阻效應，增加元件的性能外，更可以直接和以砷化鎵作 為基板材料的其他電子元件直接做結合，不但可以得到良 好的氫氣感測特性’更可以跟光電元件、功率電晶體以及 微波元件相互整合，以形成功能甚為廣泛之積體電路而確 實達到本發明之目的。 2〇 惟以上所述者，僅為本發明之較佳實施例而已，當不 能以此限定本發明實施之範圍，即大凡依本發明申請專利 範圍及發明說明書内容所作之簡單的等效變化與修飾，皆 應仍屬本發明專利涵蓋之範圍内。 【圖式簡單說明】 12 別226 玖、發明說明（8 ) 第一圖為本發明氫氣感測器之一較佳實施例之結構示 意圖； •第一圖是本發明氫氣感測器於感測到氫氣時的能帶圖 . 貫驗曲線圖，說明本發明氫氣感測器於室 >里時在不同氫氣含 里之裱境下所測量的順向電流-電壓特 ΐ生， 第四圖是一會i ㈤β、 鳅曲線圖，說明本發明氫氣感測器在室 10 度時之對應的蕭特基能障高度變化； *《實驗曲線圖，說明本發明氫氣感測器之溫 度對飽和靈敏度的影響； 第六圖是一實驗 λ。 曲線圖，說明本發明氫氣感測器於 95C時在不同氫氣含息μ四 、 里的裱境下，感測不同氫氣濃度後其 對應的電流-電壓變化特性；及 15 、第，圖疋、實驗曲線圖，說明本發明氳氣感測器在溫 度為95°C時所測量之暫態響應。 13 591226 玖、發明說明（9 ) 【圖式之主要元件代表符號簡單說明】 1氫氣感測器 14半導體歐姆接觸頂層 11半導體基板 15歐姆金屬接觸層 12半導體緩衝層 16氧化層 13半導體薄膜層 17蕭特基金屬接觸層 14591226 (1) Description of the invention [Technical field to which the invention belongs] The present invention relates to a hydrogen sensor, and particularly to a diode-type hydrogen sensor. [Previous technology] 5 Hydrogen sensors have been widely used in factories, laboratories, hospitals, and transportation vehicles to achieve the effect of early warning. At present, most of the traditional hydrogen sensors are hydrogen sensors that are passive components, and other additional equipment or conversion circuits are required to analyze or enlarge the hydrogen concentration. Therefore, the volume must be increased and the price is expensive. And cannot meet the requirements of intelligence. In terms of structure, semiconductor hydrogen sensors can be roughly divided into metal-semiconductor Schottky barrier diodes, metal-oxide layers-semiconductor Schottky barrier diodes, metal-oxide layers-semiconductor capacitors, and There are four types of metal-oxide layer-semiconductor field-effect transistor. The transistor-type hydrogen sensor is mainly based on the threshold voltage of 15 and the change in capacitance at both ends as the basis for sensing hydrogen. The production cost is higher, and the sensitivity of the sensor is also lower. 'As a polar hydrogen sensor, the relationship between the voltage and the voltage can show an exponential change in forward current, so the change in current is larger. A large hydrogen sensing sensitivity can be obtained. At the same time, its 20 reverse currents exhibit high linearity and high sensitivity. Therefore, the diode hydrogen sensor is more suitable for commercial applications. However, 疋 'one-body hydrogen sensor is generally based on Shi Xi as the main material'. The biggest disadvantage of Shi Xi material is that it cannot be used in high temperature environments and its sensitivity is low. Although, currently, gallium arsenide and phosphorus can be used. Indium, gallium nitride and 6 thallium, invention description C; 2,) ::: Compound semiconductor materials such as carborundum and sulphur, to solve this problem, but compound semiconductor materials such as Shishenhualu and indium must be in the low temperature region Only when operating, will it have greater sensitivity. Compound semiconductor materials such as gallium nitride and carbide carbides need to be operated at high temperatures. Therefore, compound semiconductor materials such as Shishenhua marry, scaly marriage, gasification recording, and obstruction to fossil clouds. Still unable to provide enough operating temperature interval 'to solve the problem of sensing sensitivity. Although 'currently known to make indium gallium halide compound semiconductor materials can provide a wide range of operating temperature operation, however, hindering the steel marry material can only be fixed under the condition that the Mole fraction of indium is 0.49. Lattice matching with the fragmented Su substrate, so there are still significant limitations. Therefore, how to increase the working temperature range and increase the sensitivity of a diode-type tritium gas sensor is a goal that the current industry and academia work together. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydrogen sensor with low leakage current and high sensing sensitivity. Therefore, a hydrogen sensor of the present invention includes a semiconductor substrate, a semiconductor buffer layer formed on the semiconductor substrate, a semiconductor thin film layer formed on the semiconductor buffer layer, and a semiconductor thin film layer. The top layer of semiconductor ohmic contact in the blade region, an ohmic metal contact layer as a cathode electrode, and a Schottky metal contact layer as an anode electrode. A 忒 ohmic metal contact layer is formed in a part of the upper area of the semiconductor ohmic contact top layer and extends downward. Up to the semiconductor ohmic contact top layer and the semiconductor thin film layer, the Schottky metal contact layer is formed in a part of the semiconductor thin film layer and is not in contact with the semiconductor ohmic contact top layer; y: "After the contact layer of the special metal is dissociated into hydrogen atoms, polarization occurs at the interface of the thin semiconductor layer to form a dipole moment layer, which changes the orientation of the Schottky barrier and changes the current of the device. Voltage characteristics to sense hydrogen concentration. [Embodiment] The foregoing and other technical contents of the present invention, The points and effects will be clearly understood in the following detailed description of one of the preferred embodiments with reference to the drawings. Referring to the first figure, a preferred embodiment of a hydrogen sensor according to the present invention is suitable for sensing. The hydrogen concentration measurement includes a semiconductor substrate u, a semiconductor buffer layer 12 formed on the semiconductor substrate 11, a semiconductor thin film layer 13 formed on the semiconductor buffer layer 12, and a partial region formed on the semiconductor thin film layer 13. A semiconductor ohmic contact top layer M, an ohmic metal contact layer 15 formed on the semiconductor ohmic contact top layer 14 and extending downward to the semiconductor ohmic contact top layer 14 and the semiconductor thin film layer 13 are formed in the semiconductor An oxide layer 16 on a part of the thin film layer 13 and not in contact with the semiconductor ohmic contact top layer 14 and a Schottky metal contact layer 17 formed on the oxide layer 16 and not in contact with the semiconductor ohmic contact top layer 14 The above-mentioned hydrogen sensor 1 uses semi-insulating gallium arsenide (GaAs) M material as the semiconductor substrate & 11, and uses metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxial growth (MBE) technology, and the use of undoped gallium arsenide (GaAs) material on the semiconductor substrate u to grow from 0.5 to 5-0 to form the semiconductor Buffer layer 12; then n-type, concentration range between 1x10ΐ5 to 5xl0iW3, Moore's fraction of 绍, invention description Γ4) 彳: / to 0.45 AixGai-xAs Material, and / or n-type indium gallium phosphide (inxGai-xp) material having a concentration range of lx1015 to 5x10i8cm-3 and an indium Moire fraction of 0.49 is grown on the semiconductor buffer layer 12 The semiconductor thin film layer 13 is formed to a thickness of 1000 to 5000 A. Next, a gallium arsenide (GaAs) material with an n-type and a concentration ranging from 1x10π to 1x1019cnf3 is selected, and the semiconductor thin film layer 13 is grown to a thickness of 100 to 3000 A in the upper region to form the semiconductor ohmic contact top layer 14. Then, using traditional photolithographic lithography and vacuum evaporation technology, gold-germanium-nickel alloy (AuGeNi) material and / or gold-germanium alloy (AuGe) are used to vapor-bond the ohmic contact top layer 14 of the semiconductor. A thickness of the alloy layer between A and _, and annealed under the environment of 40 rc for i minutes, so that the alloy layer penetrates the semiconductor ohmic contact top layer 14 and extends to the semiconductor thin film layer 13 to form the The ohmic metal contact layer 15. Then, a silicon oxide (SiO2), a titanium oxide (butylene), and / or an oxide (ZnO) are selected, and a part of the region on the semiconductor thin film layer 13 and the semiconductor are The ohmic contact top layer 14 grows to a thickness of 20 to 500 A without contact to form the oxide ^ 16; finally, platinum (pt), palladium rhenium), nickel (Ni), heteroh), and ruthenium (Ru) are selected. And / or one of silver (Ir), at the oxidation frequency of 16 igA to 2 μm, forming the Schottky metal contact layer 17 as an anode electrode to prepare the hydrogen sensor of the present invention. Chain, corrosion. _... Nickel-germanium, ruthenium, and / or iridium have good catalytic activity for hydrogen. When hydrogen molecules are adsorbed on the surface, they will be separated into hydrogen atoms. At the same time, most of the hydrogen atoms will diffuse through the Schottky metal ㈣17 'and these chlorine atoms diffuse to Schottky metal 591226 玖, Description of the invention (5) When the interface between the contact layer 17 and the oxide layer 16 is caused by polarization, a dipole moment layer is formed, and the moment of the dipole moment can change the interface between the Schottky metal contact layer 17 and the oxide layer 16. The electric field further reduces the Schottky barrier height of the metal-semiconductor interface, so the current_5 voltage characteristic of the hydrogen sensor of the present invention can be changed to achieve the purpose of sensing hydrogen. Referring to the second figure, the change in the energy band of the hydrogen sensor 1 according to the present invention when hydrogen is sensed is described. The Schottky metal contact layer 17 is made of palladium metal as a material to interact with hydrogen as an example. After the introduction of radon gas, because palladium metal has a catalytic effect on hydrogen, when hydrogen molecules are adsorbed on the surface of palladium metal, they will be dissociated into 10 hydrogen atoms, and most of the hydrogen atoms will diffuse through the palladium metal, and then A dipole moment layer is formed between the Schottky metal contact layer 17 and the oxide layer 16 interface. This moment moment layer will change the equilibrium state of the original charge distribution and reach a new equilibrium state. This new equilibrium state reduces the semiconductor The width of the empty region decreases the height of the Schottky barrier. 15 Referring to the third figure, the forward current-voltage characteristics measured by the above-mentioned hydrogen sensor 1 under different hydrogen content air, 15, 48, 97, 202, 1010, and 9090 ppm H2 / air at room temperature From the results of the curve, it can be known from the above that the larger the hydrogen content, the smaller the Schottky barrier height, so the interface current will be relatively large; from the experimental results, it can be seen that the radon sensor 1 of the present invention can perform at room temperature. A nitrogen content of 15ppm HVair was sensed, and the amount of change in current can be changed from 10-12 amps to 10 · 9 amps at a forward bias of 0.2 volts, and has a very high sensing ability. The fourth figure is the experimental result of recording the change in the height of the Schottky barrier of different nitrogen concentrations of the hydrogen sensor 1 of the present invention at room temperature. From this figure, it is obvious that 10 591226 发明, description of the invention (6) The higher the hydrogen concentration, the greater the change in the height of the energy barrier caused. The fifth figure is the experimental result of the influence of the temperature of the hydrogen sensor 1 of the present invention on the saturation sensitivity. The saturation sensitivity s is defined as the ratio of the current change amount to the reference current, that is, (\ -1 4) / 4, where I ", Iair are the current values in the 5th ring of hydrogen, and the current in the oxygen. From this figure, it can be seen that the sensitivity of the hydrogen subtractor 1 of the present invention increases as the hydrogen content increases, and the room temperature and forward bias are Under the environment of 0.35V and 9090ppm hydrogen content, the saturation sensitivity is as high as 156, and as the temperature increases, the saturation sensitivity becomes smaller as the change in the height of the energy barrier becomes smaller. 10 The sixth figure is the hydrogen of the present invention Current-voltage characteristics of sensor 1 measured at 95 ° C under different hydrogen-containing tritium, 15, 97, 1010, and 9900Ppm H2 / air), under forward bias At this time, the current exhibits an exponential change. There is still a hundred times the amount of change when the forward bias is 0.2 volts, and it shows a linear change when the reverse bias is applied. The sensor i is still quite obvious under high temperature conditions. It is quite stable in application. Referring to the seventh figure, the experimental results of the transient response measured by the hydrogen sensor 1 of the present invention at a temperature of 95 ° C, the points a and b shown in the figure represent the introduction of nitrogen and The instantaneous operating point when hydrogen is closed. When hydrogen is introduced, 20 represents air of different hydrogen content, and flows into the test chamber at a rate of 500ml / min. The test conditions are to maintain _ fixed forward bias Mvf = (). 35v, due to dissociation The hydrogen atom forms a dipole moment, and the current increases rapidly due to the introduction of nitrogen. On the other hand, when the hydrogen is turned off, the sensor is directly exposed to the air. Yu Xiao 11 591226 发明, description of the invention (7) The surface of the special metal contact layer 17 caused the recovery of the corresponding current. If the reaction time is defined as the time required to reach a stable value, the graph can be seen that the present invention's hydrogen sensing The reaction time of device 1 is about 302 (15ppm H2 / aii〇, 40.3 (202ppm H2 / air), 13.2 (1010ppm H2 / air), 5 and 4.5 seconds (9090PPm H2 / air). Invention of hydrogen sensor When it is high, the probability of collision is relatively high, and the change in current is greater, which means more sensitive. In summary, because the aluminum gallium arsenide (AlGaAs) material has a larger energy gap and matches the gallium arsenide lattice Advantages, so that the hydrogen sensor 10 of the present invention 1 uses a semi-insulating gallium arsenide (GaAs) material as the semiconductor substrate u, and grows into a semiconductor thin film layer 13 with materials such as aluminum gallium arsenide and indium gallium phosphide, and Selecting n-type gallium arsenide (GaAs) as the semiconductor ohmic contact top layer 14, so it is very flexible in engineering design and application; Moreover, the semiconductor ohmic contact top layer 14 of the hydrogen sensor 1 of the present invention can reduce the resistance effect by 15 In addition to increasing the performance of the device, it can also be directly combined with other electronic components using gallium arsenide as the substrate material, not only can get good hydrogen sensing characteristics, but also can be integrated with optoelectronic components, power transistors and microwave components. In order to form an integrated circuit with a wide range of functions, the purpose of the present invention is indeed achieved. 20 However, the above are only the preferred embodiments of the present invention. When the scope of implementation of the present invention cannot be limited by this, that is, the simple equivalent changes made according to the scope of the patent application and the content of the invention specification of the present invention, and Modifications should still fall within the scope of the invention patent. [Brief description of the drawing] 12 226 玖, description of the invention (8) The first picture is a schematic diagram of the structure of a preferred embodiment of the hydrogen sensor of the present invention; • The first picture is the hydrogen sensor of the present invention in the sensing Energy band diagram when reaching hydrogen. The perforation curve diagram illustrates the forward current-voltage characteristics measured by the hydrogen sensor of the present invention in a chamber > It is a graph of i ㈤β, 鳅 for a while, illustrating the change in the height of the corresponding Schottky barrier of the hydrogen sensor of the present invention when the chamber is at 10 degrees; * "Experimental curve showing the temperature versus saturation of the hydrogen sensor of the present invention The effect of sensitivity; the sixth figure is an experimental λ. A graph illustrating the current-voltage change characteristics of the hydrogen sensor of the present invention after different hydrogen concentrations are sensed under the conditions of different hydrogen contents μ4 and li at 95C; and 15, FIG. The experimental curve diagram illustrates the transient response measured by the radon sensor of the present invention when the temperature is 95 ° C. 13 591226 发明 Description of the invention (9) [Simplified description of the main symbols of the drawings] 1 Hydrogen sensor 14 Top layer of semiconductor ohmic contact 11 Semiconductor substrate 15 Ohmic metal contact layer 12 Semiconductor buffer layer 16 Oxide layer 13 Semiconductor thin film layer 17 Schottky metal contact layer 14