Recessed gate GaN MESFETs fabricated by the photoelectrochemical etching process
- PDF / 1,266,073 Bytes
- 7 Pages / 417.6 x 639 pts Page_size
- 36 Downloads / 202 Views
Seocho-gu, Seoul, Korea 137-724 Inorganic Materials Eng., Myongji University, 38-2 Nam-Dong, Yongin-Si, Kyunggi-Do, Korea ***Department of Electronic Materials Eng., Kwang Woon University, 447-1 Wolgye-Dong, Seoul, Korea
"**Department of
Abstract A new photo-electrochemical etching method was developed and used to fabricate GaN MESFETs. The etching process uses photoresist for masking illumination and the etchant is KOH based. The etching rate with 1.0 mol% of KOH for n-GaN is as high as 1600 A/min under the Hg illumination of 35 mW/cm2. The MESFET saturates at VDs = 4 V and pinches off at VGs = -3 V. The maximum drain current of the device is 230 mA/mmn at 300 K and the value is remained almost same for 500 K operation. The characteristic frequencies, fT and fmx, are 6.35 GHz and 10.25 GHz, respectively. Insensitivity of the device performance to temperature was attributed to the defect-related high activation energy of dopants for ionization and band-bending at the subgrain boundaries in GaN thin films. 1. INTRODUCTION Wide bandgap semiconductors based upon the 11I-Nitride system, which are mainly developed for optical application, have many properties which are ideal for electronic devices for high temperature, high frequency, high power, and radiation hard application. A variety of high frequency electronic devices can be fabricated from GaN-based semiconductors; these devices are predicted to offer superior DC and RF performance compared to more conventional Si and GaAs devices from the view point of high power. Theoretical calculations for GaN MESFET predict output power density near 5 W/mm, power-added efficiency higher than 50 %, and linear power gain about 20 dB for an optimized device structure [1]. In addition, GaN can allow for the AlGaN/GaN heterostructures which was demonstrated to produce two-dimensional electron gas (2 DEG) and thus makes possible several novel devices that can operate at frequencies beyond the capability of SiC devices. Also, the 2 DEG permits low resistances and low noise performance not possible with SiC [2]. Despite the excellent electronic properties of GaN, the fabrication of GaN MESFETs with novel designs have been hindered by the chemical inertness of this material. Thus, the most successful etching process so far has been dry etching method including reactive ion etching (RIE) [3], electron cyclotron resonance (ECR) RIE [4], and inductively coupled plasma (ICP) RIE [5]. However, these techniques are known to result in ion-induced damage on the etch surface which is highly undesirable for the high frequency and high power operation of devices. Wet chemical etching is a desirable substitute for dry etching method by providing low damage on the surface of the active region. There has been a report on the photoelectrochemical wet etching process for GaN films using KOH solution under the illumination of Hg arc lamp [6]. However, the experiment was performed using Ti metal mask which is not normally used in conventional wet etching process and is not suitable for the fabricati
Data Loading...
