Interfacial and electrical characteristics of a HfO ₂ /n–InAlAs MOS-capacitor with different dielectric thicknesses

Abstract

A HfO 2 /n-InAlAs MOS-capacitor has the advantage of reducing the serious gate leakage current when it is adopted in InAs/AlSb HEMT instead of the conventional Schottky-gate. In this paper, three kinds of HfO 2 /n-InAlAs MOS-capacitor samples with different HfO 2 thickness values of 6, 8, and 10 nm are fabricated and used to investigate the interfacial and electrical characteristics. As the thickness is increased, the equivalent dielectric constant ε ox of HfO 2 layer is enhanced and the InAlAs-HfO 2 interface trap density D it is reduced, leading to an effective reduction of the leakage current. It is found that the HfO 2 thickness of 10 nm is a suitable value to satisfy the demands of most applications of a HfO 2 /n-InAlAs MOS-capacitor, with a sufficiently low leakage current compromised with the threshold voltage.

Study on the Physical and Leakage Current Characteristics of an Optimized High-k/InAlAs MOS Capacitor with a HfO2–Al2O3 Laminated Dielectric

“…The structure diagram of the MOS capacitor is shown in Figure 1. To match with InAlAs and achieve better performance, InP was selected as the substrate rather than GaAs, which were frequently used in other studies [7][8][9]. InP is semi-insulating and a 350-µm-thick substrate was used.…”

“…Because of its good compatibility with AlSb, InAs, and InGaAs, InAlAs is one of the most promising materials for the protection layer of InAs/AlSb and InAlAs/InGaAs HEMTs to enhance the carrier density in the channel [1,3]. Depositing a high-k dielectric film on InAlAs as a MOS capacitor can effectively suppress the leakage current [5][6][7][8][9]. However, the lack of reasonable high-k dielectrics is still a major problem that limits the performance of the isolated gate.…”

“…However, the lack of reasonable high-k dielectrics is still a major problem that limits the performance of the isolated gate. HfO 2 is the main candidate for the high-k dielectric because of its high dielectric constant [5,7], but its direct deposition on InAlAs limits its performance owing to the poor lattice match with InAlAs [8]. Therefore, a thin Al 2 O 3 film inserted between InAlAs and HfO 2 as a buffer layer has been proposed [8].…”

Исследование плотности интерфейсных состояний на границах раздела диэлектрик / In-=SUB=-0.52-=/SUB=-Al-=SUB=-0.48-=/SUB=-As

“…Плотность интерфейсных состояний на границе раздела диэлектрик/InAlAs, сформированной методом атомно-слоевого осаждения (АСО) high-k диэлектриков HfO 2 или Al 2 O 3 на поверхность InAlAs после проведения различных химических обработок, изучалась в [8][9][10][11]. Во всех работах при анализе импеданса структур металл−диэлектрик−полупроводник (МДП) была получена D it более 10 12 eV −1 · cm −2 .…”

“…Они слабо изменяются по ширине запрещенной зоны InAlAs в пределах (3−6) · 10 11 и (1−3) · 10 11 eV −1 · cm −2 для границ раздела со слоями Al 2 O 3 и SiO 2 соответственно. Данные значения существенно меньше, чем приведенные в работах [8][9][10][11]. Полученные результаты показывают, что наблюдаемые различия величин D it могут быть связаны как с технологическими особенностями формирования границы раздела диэлектрик/InAlAs, так и с особенностями измерения ВФХ МДП-структур на основе InAlAs.…”