以AlAsSb材料改善InP蕭基能障高之研究

Abstract

InP及其它III/V化合物半導體之中的高能障高蕭基接觸對元件製程而言非 常重要,傳統上,因費米針扎效應造成反向飽和電流過大而限制了InP材料 的應用,過去曾有許多提升InP蕭基能障高的嘗試,但通常都因為不佳的金 屬-半導體接面而使得能障之提升經不起時間的考驗。在我們的研究中,藉 一全新的材料AlAsSb改善n-InP之蕭基能障高,其結構是先在n-InP基板上 成長一n-InP之緩衝層,之後是AlAsSb能障層,緊接著成長n-InP之覆蓋層, 最後蒸鍍上蕭基接觸,並以電壓-電流(I-V)及電容-電壓(C-V)量測來探討 其電性及介面之特性。對一300埃厚的InP覆蓋層之蕭基元件中,當AlAsSb 厚度自0增加至1000埃時,能障高自0.45增加至0.76eV,若繼續增加AlAsSb 厚度反而會使得元件特性下降,當AlAsSb厚度自1000增至2000埃時,能障高 自0.76減至 0.72eV,同時,實驗顯示當覆蓋層厚度自900減至350埃時,能障 高將增加 ,覆蓋層厚度對蕭基能障高之決定有深遠的影響,我們發現當覆 蓋層厚度減少,能障高增加。 The formation of reliable high Schottky barrier height contact to InP and III/Vcompound semiconductor is very important for device fabrication.Fermi level pinning traditionally has restricted the application of InP because of its large reverse leakage current.Many attempts have been made to realized a large barrier height.However,a poor intreface leads to problems with long term stability. In our study,we used a new material AlAsSb to improve the Schottky barrier height of n-InP material. The Schottky diode structure is made of n-InP cap layer grown on an AlAsSb layer,with an n-InP buffer layer on top of n-InP substrate Finally,a Schottky contact was deposited.The electrical and interface properties of this diode were studied by I-V and C-V techniques. For a 0.03um-thick-InP-cap-layer Schottky diode,the barrier height was found to increase from 0.45 to 0.76eV as AlAsSb thickness increased from thickness 0 to 0.1um.However,further increasing AlAsSb intermediate layer degrade the device performance.The barrier height decreased from .76 to .72eV for AlAsSb thickness changed from 0.1 to 0.2um.It also shows that when the cap layer thickness decreased from .09 to .035 um,the effective barrier height will increase. In addtion thickness of cap layer also has a profound effect in determing the Schottky barrier height.We found that the barrier is increased as the cap layer is decreased.