InGaP/GaAs HBT implantation leakage current and electrical breakdown

✍ Scribed by Hong Shen; A.M Arrale; Peter Dai; Shiban Tiku; Ravi Ramanathan

• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 266 KB
• Volume: 7
• Category: Article
• ISSN: 1369-8001
• DOI: 10.1016/j.mssp.2004.05.003

✦ Synopsis

Implantation of HBT by helium ions has been an accepted means for achieving the desired low leakage currents. In the past, two implant steps of doses 1E+14 and 4E+13 ions/cm 2 , at energies 200 and 400 KeV, respectively, were shown to adequately isolate the HBT. The present work shows a medium dose (4E+13 ions/cm 2 ) of the low-energy implant can result in an isolation resistance an order of magnitude higher than that of a high-dose implant. As a result, the leakage current is reduced. However, the breakdown voltage is also lower compared to its value at higher dose. Tunneling breakdown has been confirmed as being the major contributor to the observed breakdown, by its negative temperature coefficient. In addition, infrared (IR) emission imaging also showed that impact ionization may be playing a role for breakdown at higher electrical field. It is proposed that large As vacancies generated by helium ions makes the GaAs epitaxial layer more p-type compared to the highly doped n + -GaAs, where the collector contact is built on, thus causing it to display a weak diode-like behavior. Finally, the temperature and dose dependences of both the leakage current and the breakdown voltage will be discussed in the context of damage accumulation and junction characteristics.